diff --git a/FCCee/IDEA/compact/IDEA_o1_v03/DectDimensions_IDEA_o1_v03.xml b/FCCee/IDEA/compact/IDEA_o1_v03/DectDimensions_IDEA_o1_v03.xml
index 3a6e0fd32..31878b65e 100644
--- a/FCCee/IDEA/compact/IDEA_o1_v03/DectDimensions_IDEA_o1_v03.xml
+++ b/FCCee/IDEA/compact/IDEA_o1_v03/DectDimensions_IDEA_o1_v03.xml
@@ -56,6 +56,7 @@
     <constant name="DetID_FiberDRCalo"             value=" 25"/>
 
     <constant name="DetID_muonSystem"       value=" 26"/>
+    <constant name="DetID_Preshower"       value=" 27"/>
 
     <!-- BPW: Beam Pipe Width -->
     <constant name="BPWWall"       value="0.35*mm" />
@@ -205,6 +206,16 @@
     <constant name="tracker_region_zmax" value="DCH_half_length_total"/>
     <constant name="tracker_region_rmax" value="DCH_outer_cyl_R_total"/>
 
+    <!-- Pre-shower Parameters-->
+    <constant name = "psNumSides"                              value = "32"/>        <!-- The number of sides of the pre-shower --> 
+                                                <!-- Barrel -->
+    <constant name = "psBarrelFirstLayerRadius"                     value = "2440*mm"/>  <!-- 1st Barrel microRWELL detector inner radius-> its the start point of thicknesses of the microRWELL material. In our case the shape is Polygon, so the radius is in the middle of the polygon side. -->
+    <constant name = "psBarrelLength"                               value = "5100*mm"/> <!--Barrel detector length, in the description of the detctor we always use the half-length -->      
+                                                <!-- Endcap -->
+    <constant name = "psEndcapFirstLayerZOffset"                     value = "2550*mm"/>  <!-- 1st Endcap microRWELL detector inner ZOffset-> its the start point of thicknesses of the microRWELL volume -->
+    <constant name = "psEndcapLayersInnerRadius"                    value = "390*mm"/> <!--Endcap detector inner radius, its the start point of thicknesses of the detector material ** it applies for both detector layers and yoke-->
+    <constant name = "psEndcapLayersOuterRadius"                    value = "2430*mm"/> <!--Endcap detector outer radius, its the end point of thicknesses of the detector material ** it applies for both detector layers and yoke-->
+      
     <!-- Fiber dual-readout calorimeter tower dim-->
     <constant name="FiberDRCalo_world_outer_radius" value="4525.*mm"/>
     <constant name="FiberDRCalo_world_inner_radius" value="252.*mm"/>
@@ -220,9 +231,7 @@
     <constant name="FiberDRCalo_endcap_nphi"         value="144"/>
 
     <!-- Muon System Parameters-->
-
     <constant name = "numberOfSides"                              value = "8"/>        <!-- The number of sides of the muon system e.g (Octagon, Hexagon, ...)--> 
-
                                                 <!-- Barrel -->
     <constant name = "BarrelFirstLayerRadius"                     value = "4500*mm"/>  <!-- 1st Barrel microRWELL detector inner radius-> its the start point of thicknesses of the microRWELL material. In our case the shape is Polygon, so the radius is in the middle of the polygon side. -->
     <constant name = "BarrelLength"                               value = "9000*mm"/> <!--Barrel detector length, in the description of the detctor we always use the half-length -->      
@@ -230,10 +239,7 @@
     <constant name = "EndcapFirstLayerZOffset"                     value = "4500*mm"/>  <!-- 1st Endcap microRWELL detector inner ZOffset-> its the start point of thicknesses of the microRWELL volume -->
     <constant name = "EndcapLayersInnerRadius"                    value = "700*mm"/> <!--Endcap detector inner radius, its the start point of thicknesses of the detector material ** it applies for both detector layers and yoke-->
     <constant name = "EndcapLayersOuterRadius"                    value = "5320*mm"/> <!--Endcap detector outer radius, its the end point of thicknesses of the detector material ** it applies for both detector layers and yoke-->
-      
     <!-- End of Muon system Parameters-->
-        
-
   </define>
   
   
diff --git a/FCCee/IDEA/compact/IDEA_o1_v03/Preshower_o1_v01.xml b/FCCee/IDEA/compact/IDEA_o1_v03/Preshower_o1_v01.xml
index 633a86142..9505f04c8 100644
--- a/FCCee/IDEA/compact/IDEA_o1_v03/Preshower_o1_v01.xml
+++ b/FCCee/IDEA/compact/IDEA_o1_v03/Preshower_o1_v01.xml
@@ -3,7 +3,7 @@
 
   <info name="pre-shower"
 	title=" detailed version of IDEA pre-shower system for FCC-ee"
-	author="Nitika Nitika and Mahmoud Ali- mahmoud.ali@cern.ch"
+	author="Nitika Nitika- nitika.nitika@cern.ch, Mahmoud Ali- mahmoud.ali@cern.ch"
 	url="no"
 	status="development"
 	version="2.0">
@@ -29,8 +29,6 @@
        <constant name = "overlapingY"                           value = "5*mm"/> <!-- the common distance between mRWELL chambers in Y direction -->
        <constant name = "overlapingZ"                           value = "5*mm"/> <!-- the common distance between mRWELL chambers in Z direction -->
        <constant name = "clearance"                             value = "1*mm"/> <!-- it's a small distance to be used to avoid overlapping between the different volumes ~ 1 mm -->
-     <!-- %%%%%%                      Iron yoke thickness                %%%%%% -->
-      <constant name = "YokeThickness"                          value = "300*mm"/>  
   </define>   
 
   <readouts>
@@ -42,14 +40,14 @@
 
   <detectors>
     <!-- mRWELL envelope -->
-    <detector name="Preshower" type="muonSystemMuRWELL_o1_v01" id="33" readout="PreshowerSystemCollection">
+    <detector name="Preshower" type="muonSystemMuRWELL_o1_v01" id="DetID_Preshower" readout="PreshowerSystemCollection">
       <dimensions x="mRWELLTotalThickness/2.0" y="mRWELLYLength" z="mRWELLZLength" x_offset="0*mm" y_offset="0*mm" z_offset="0*mm" material="Air"/>
       <sensitive type="tracker"/>
 
       <!-- Specify the detector parameters and the overlap /// if you want exclude any component, e.g: endcap, just put endcapDetectorParameters=0   // radius is put in the middle, so its not the inner neither the outer -->
-      <generalParameters numSides="32" overlapY="overlapingY" overlapZ="overlapingZ" clearance="clearance"/>
-      <Barrel numDetectorLayers ="1"  rmin="2440*mm" length="5100*mm" numYokes="0" yoke_Thickness="0*mm" yoke_Material="G4_Fe"/> 
-      <Endcap numDetectorLayers="1"  rmin="390*mm" rmax="2430*mm" z_offset="2550*mm" numYokes="0" yoke_Thickness="0*mm" yoke_Material="G4_Fe" />
+      <generalParameters numSides="psNumSides" overlapY="overlapingY" overlapZ="overlapingZ" clearance="clearance"/>
+      <Barrel numDetectorLayers ="1"  rmin="psBarrelFirstLayerRadius" length="psBarrelLength" numYokes="0" yoke_Thickness="0*mm" yoke_Material="G4_Fe"/> 
+      <Endcap numDetectorLayers="1"  rmin="psEndcapLayersInnerRadius" rmax="psEndcapLayersOuterRadius" z_offset="psEndcapFirstLayerZOffset" numYokes="0" yoke_Thickness="0*mm" yoke_Material="G4_Fe" />
 
       <!-- mRWELL chamber -->
       <!-- note: all thicknesses are half-lengths -->
@@ -66,4 +64,4 @@
     </detector>
   </detectors>
 
-</lccdd>
+</lccdd>
\ No newline at end of file
diff --git a/detector/muonSystem/muonSystemMuRWELL_o1_v01.cpp b/detector/muonSystem/muonSystemMuRWELL_o1_v01.cpp
index 55f734fa6..abf64a9c9 100644
--- a/detector/muonSystem/muonSystemMuRWELL_o1_v01.cpp
+++ b/detector/muonSystem/muonSystemMuRWELL_o1_v01.cpp
@@ -85,10 +85,13 @@ static dd4hep::Ref_t createmuonSystemMuRWELL_o1_v01(dd4hep::Detector& lcdd,
   double rectangleThickness = (2 * dimensions.y()) * std::sin(chamberAngle_rad) + (2 * dimensions.x()) * std::cos(chamberAngle_rad) + 1.2 * clearance;
   double rectangleAngle_rad = std::atan(rectangleThickness/dimensions.z());
   double detectorVolumeThickness;
+  double endcapDetectorEnvZ;  // endcap detetcor layer thickness
   if (sideLengthEstimate <= (2 * dimensions.y()) && numBarrelDetectorLayers == 1){      // putting this condtition to minimize the volume thickness in case of there is only one chamber per side(espicially for circular shape detector)
-    detectorVolumeThickness = rectangleThickness + 2 * clearance;
+    detectorVolumeThickness = rectangleThickness * 1.33;  // multiplying by 1.33 fit the best thickness avoiding overlaps with smaller volumes insides (rectangles).
+    endcapDetectorEnvZ = 2 * detectorVolumeThickness; 
   } else {
     detectorVolumeThickness = (2 * dimensions.z()) * std::sin(rectangleAngle_rad) + rectangleThickness * std::cos(rectangleAngle_rad);
+    endcapDetectorEnvZ = detectorVolumeThickness;
   }
 
   double endcapDetectorSideLength = (2 * (endcapDetectorLayerInnerRadius + 2 * dimensions.y()) * std::tan(shapeAngle_radians)) + 2 * clearance; 
@@ -107,11 +110,9 @@ static dd4hep::Ref_t createmuonSystemMuRWELL_o1_v01(dd4hep::Detector& lcdd,
 
   double endcapRemainderZ = std::fmod((endcapDetectorYLength - 2 * clearance), (2 * dimensions.z() - overlapZ)) / (2 * dimensions.z()) - (2 * clearance / dimensions.z());
 
-  double endcapDetectorEnvZ = detectorVolumeThickness;  // layer thickness
-
   double barrelRMax = radius + numBarrelDetectorLayers * (2 * detectorVolumeThickness) + numBarrelRadiators * barrelRadiatorThickness;
   double barreltotalLength = barrelLength + (numEndcapDetectorLayers * 2) * (2 * detectorVolumeThickness) + (numEndcapRadiators * 2) * endcapRadiatorThickness; // This condition to make the last barrel layer encloses all the endcap layers inside it.
-  double EndcaptotalLength = numEndcapDetectorLayers * (2 * detectorVolumeThickness) + numEndcapRadiators * endcapRadiatorThickness;
+  double EndcaptotalLength = numEndcapDetectorLayers * (2 * endcapDetectorEnvZ) + numEndcapRadiators * endcapRadiatorThickness;
   double endcapOffset = endcapZOffset + EndcaptotalLength/2.0;
 
   int barrelIdCounter = 1;
@@ -673,9 +674,9 @@ static dd4hep::Ref_t createmuonSystemMuRWELL_o1_v01(dd4hep::Detector& lcdd,
     std::string endcapDetectorEnvelopeName;
     double endcapDetectorEnvZPos;
 
-    dd4hep::PolyhedraRegular  endcapDetectorEnvelope(numSides, endcapDetectorLayerInnerRadius, endcapDetectorLayerOuterRadius, 2 * detectorVolumeThickness);
+    dd4hep::PolyhedraRegular  endcapDetectorEnvelope(numSides, endcapDetectorLayerInnerRadius, endcapDetectorLayerOuterRadius, 2 * endcapDetectorEnvZ);
 
-    endcapLayerZOffset = - EndcaptotalLength/2.0 + detectorVolumeThickness + numEndcapLayer * (2 * detectorVolumeThickness) + numEndcapLayer * endcapRadiatorThickness;  // Automation of inner Z-Offset of different layers, taking into account that every detector layer is followed by a yoke(radiator) layer
+    endcapLayerZOffset = - EndcaptotalLength/2.0 + endcapDetectorEnvZ + numEndcapLayer * (2 * endcapDetectorEnvZ) + numEndcapLayer * endcapRadiatorThickness;  // Automation of inner Z-Offset of different layers, taking into account that every detector layer is followed by a yoke(radiator) layer
     endcapDetectorEnvelopeName = name + "-EndcapDetectorLayer" + std::to_string(numEndcapLayer + 1);
     endcapDetectorEnvZPos = endcapLayerZOffset; 
 
@@ -698,8 +699,8 @@ static dd4hep::Ref_t createmuonSystemMuRWELL_o1_v01(dd4hep::Detector& lcdd,
     for (int side = 0; side < numSides; ++side) {
 
       int sideID = (numEndcapLayer + 1) * 100 + (side +1);  // to differentiated with the same side in different layers.
-      dd4hep::Trapezoid endcapDetectorSideTrap(endcapDetectorEnvZ/2.0, endcapDetectorEnvZ/2.0, endcapDetectorSideLength/2.0, endcapDetectorSideTrapLength/2.0, endcapDetectorSideTrapYLength/2.0);
-      dd4hep::Box endcapDetectorSideBox(endcapDetectorEnvZ/2.0, endcapDetectorSideBoxLength/2.0, endcapDetectorSideBoxYLength/2.0);
+      dd4hep::Trapezoid endcapDetectorSideTrap(detectorVolumeThickness/2.0, detectorVolumeThickness/2.0, endcapDetectorSideLength/2.0, endcapDetectorSideTrapLength/2.0, endcapDetectorSideTrapYLength/2.0);
+      dd4hep::Box endcapDetectorSideBox(detectorVolumeThickness/2.0, endcapDetectorSideBoxLength/2.0, endcapDetectorSideBoxYLength/2.0);
 
       double boxOffsetZ = endcapDetectorYLength/2.0;
 
@@ -727,31 +728,44 @@ static dd4hep::Ref_t createmuonSystemMuRWELL_o1_v01(dd4hep::Detector& lcdd,
 
       double endcapDetectorSideEnvXPos = endcapDetectorXOffset ; 
       double endcapDetectorSideEnvYPos = endcapDetectorYOffset ;   
-      double endcapDetectorSideEnvZPos = - endcapDetectorEnvZ/2.0 ;   
-      double endcapDetectorSideEnvZPos2 = endcapDetectorEnvZ/2.0;
-
-     // ---------  here I start to divide the two z-positions // by odd and even numbers
+      double endcapDetectorSideEnvZPos;
+      double endcapDetectorSideEnvZPos2;
 
       dd4hep::Position endcapDetectorSideEnvTrans;
       dd4hep::PlacedVolume endcapDetectorSideEnvPhys;
       dd4hep::DetElement endcapDetectorSideEnvDE;
 
-      if (side % 2 == 0) {
+      if (sideLengthEstimate <= (2 * dimensions.y())){ // in case of small side's length, put the sides in 4 differnet positions, to avoid overlaps between different sides, and the probability increases for small sides
+        endcapDetectorSideEnvZPos = -endcapDetectorEnvZ/4.0;
+        endcapDetectorSideEnvZPos2 = -endcapDetectorEnvZ * 3.0/4.0;
+        double endcapDetectorSideEnvZPos3 = endcapDetectorEnvZ/4.0;
+        double endcapDetectorSideEnvZPos4 = endcapDetectorEnvZ * 3.0/4.0;
+
+        if (side % 4 == 0) {
+          endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos);
+        } else if (side % 4 == 1) {
+          endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos2);
+        } else if (side % 4 == 2) {
+          endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos3);
+        } else {
+          endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos4);
+        }
 
-        endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos);
-        endcapDetectorSideEnvPhys = endcapDetectorEnvVol.placeVolume(endcapDetectorSideEnvVol, dd4hep::Transform3D(endcapDetectorRotation * dd4hep::RotationY(90.0 * dd4hep::degree) , endcapDetectorSideEnvTrans));
-        endcapDetectorSideEnvDE = dd4hep::DetElement(endcapDetectorEnvelopeDE, endcapDetectorSideEnvName + "DE", sideID);
-        endcapDetectorSideEnvDE.setPlacement(endcapDetectorSideEnvPhys);
-        endcapDetectorSideEnvVol.setVisAttributes(lcdd, xmlDet.visStr());
+      } else { // else, put the sides in 2 differnet positions.
+        endcapDetectorSideEnvZPos = -endcapDetectorEnvZ/2.0;
+        endcapDetectorSideEnvZPos2 = endcapDetectorEnvZ/2.0;
 
-      } else {
+        if (side % 2 == 0) {
+          endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos);
+        } else {
+          endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos2);
+        }  
+      }    
 
-        endcapDetectorSideEnvTrans = dd4hep::Position(endcapDetectorSideEnvXPos, endcapDetectorSideEnvYPos, endcapDetectorSideEnvZPos2);
-        endcapDetectorSideEnvPhys = endcapDetectorEnvVol.placeVolume(endcapDetectorSideEnvVol, dd4hep::Transform3D(endcapDetectorRotation * dd4hep::RotationY(90.0 * dd4hep::degree) , endcapDetectorSideEnvTrans));
-        endcapDetectorSideEnvDE = dd4hep::DetElement(endcapDetectorEnvelopeDE, endcapDetectorSideEnvName + "DE", sideID);
-        endcapDetectorSideEnvDE.setPlacement(endcapDetectorSideEnvPhys);
-        endcapDetectorSideEnvVol.setVisAttributes(lcdd, xmlDet.visStr());
-      }
+      endcapDetectorSideEnvPhys = endcapDetectorEnvVol.placeVolume(endcapDetectorSideEnvVol, dd4hep::Transform3D(endcapDetectorRotation * dd4hep::RotationY(90.0 * dd4hep::degree) , endcapDetectorSideEnvTrans));
+      endcapDetectorSideEnvDE = dd4hep::DetElement(endcapDetectorEnvelopeDE, endcapDetectorSideEnvName + "DE", sideID);
+      endcapDetectorSideEnvDE.setPlacement(endcapDetectorSideEnvPhys);
+      endcapDetectorSideEnvVol.setVisAttributes(lcdd, xmlDet.visStr());
 
      // ----- dividing the trapezoid envelope to smaller pieces (rectangles)
 
@@ -952,7 +966,7 @@ static dd4hep::Ref_t createmuonSystemMuRWELL_o1_v01(dd4hep::Detector& lcdd,
 
   for (int numEndcapRadiatorLayer = 0; numEndcapRadiatorLayer < numEndcapRadiators; ++numEndcapRadiatorLayer){
 
-    double endcapRadiatorLayerZOffset = - EndcaptotalLength/2.0 + (endcapRadiatorThickness/2.0) + (numEndcapRadiatorLayer +1) * (2 * detectorVolumeThickness) + numEndcapRadiatorLayer * endcapRadiatorThickness;  // Automation of inner Z-Offset of different layers, taking into account that every detector layer is followed by a yoke(radiator) layer
+    double endcapRadiatorLayerZOffset = - EndcaptotalLength/2.0 + (endcapRadiatorThickness/2.0) + (numEndcapRadiatorLayer +1) * (2 * endcapDetectorEnvZ) + numEndcapRadiatorLayer * endcapRadiatorThickness;  // Automation of inner Z-Offset of different layers, taking into account that every detector layer is followed by a yoke(radiator) layer
 
     dd4hep::PolyhedraRegular  endcapRadiatorEnvelope(numSides, endcapRadiatorLayerInnerRadius, endcapRadiatorLayerOuterRadius, endcapRadiatorThickness);
     std::string endcapRadiatorEnvelopeName = name + "-EndcapRadiatorLayer" + std::to_string(numEndcapRadiatorLayer + 1);