diff --git a/tests/merkle_set.py b/tests/merkle_set.py
index e71ffad9..75fa456b 100644
--- a/tests/merkle_set.py
+++ b/tests/merkle_set.py
@@ -45,7 +45,7 @@
 MIDDLE = bytes([2])
 TRUNCATED = bytes([3])
 
-BLANK = bytes32([0] * 32)
+BLANK = bytes32.zeros
 
 prehashed: Dict[bytes, _Hash] = {}
 
diff --git a/tests/test_merkle_set.py b/tests/test_merkle_set.py
index 08034a28..595abd98 100644
--- a/tests/test_merkle_set.py
+++ b/tests/test_merkle_set.py
@@ -66,7 +66,7 @@ def check_tree(leafs: List[bytes32]) -> None:
         )
 
     for i in range(256):
-        item = bytes32([i] + [2] * 31)
+        item = bytes32.fill(i.to_bytes(), fill=b"\x02", align="<")
         py_included, py_proof = py_tree.is_included_already_hashed(item)
         assert not py_included
         ru_included, ru_proof = ru_tree.is_included_already_hashed(item)
diff --git a/tests/test_sized_bytes.py b/tests/test_sized_bytes.py
new file mode 100644
index 00000000..26c2484e
--- /dev/null
+++ b/tests/test_sized_bytes.py
@@ -0,0 +1,37 @@
+import pytest
+
+from chia_rs.sized_bytes import bytes8
+
+
+def test_fill_empty() -> None:
+    assert bytes8.fill(b"", b"\x01") == bytes8([1, 1, 1, 1, 1, 1, 1, 1])
+
+
+def test_fill_non_empty_with_single() -> None:
+    assert bytes8.fill(b"\x02", b"\x01") == bytes8([1, 1, 1, 1, 1, 1, 1, 2])
+
+
+def test_fill_non_empty_with_double() -> None:
+    assert bytes8.fill(b"\x02\x02", b"\x01\x01") == bytes8([1, 1, 1, 1, 1, 1, 2, 2])
+
+
+def test_fill_needed_with_0_length_fill_raises() -> None:
+    with pytest.raises(ValueError):
+        bytes8.fill(b"\x00", fill=b"")
+
+
+def test_fill_not_needed_with_0_length_fill_works() -> None:
+    blob = b"\x00" * 8
+    assert bytes8.fill(blob, fill=b"") == bytes8(blob)
+
+
+def test_fill_not_multiple_raises() -> None:
+    with pytest.raises(ValueError):
+        bytes8.fill(b"\x00", fill=b"\x01\x01")
+
+def test_align_left() -> None:
+    assert bytes8.fill(b"\x01", fill=b"\x02", align="<") == bytes8([1, 2, 2, 2, 2, 2, 2, 2])
+
+def test_invalid_alignment() -> None:
+    with pytest.raises(ValueError):
+        bytes8.fill(b"", fill=b"\x00", align="|")
diff --git a/wheel/python/chia_rs/sized_byte_class.py b/wheel/python/chia_rs/sized_byte_class.py
index 6dcbeb11..8467b88e 100644
--- a/wheel/python/chia_rs/sized_byte_class.py
+++ b/wheel/python/chia_rs/sized_byte_class.py
@@ -78,6 +78,27 @@ def random(
     def secret(cls: Type[_T_SizedBytes]) -> _T_SizedBytes:
         return cls.random(r=system_random)
 
+    @classmethod
+    def fill(cls: Type[_T_SizedBytes], blob: bytes, fill: bytes, align: Literal["<", ">"] = ">") -> _T_SizedBytes:
+        if len(blob) == cls._size:
+            return cls(blob)
+
+        fill_length = len(fill)
+        if fill_length == 0:
+            raise ValueError("fill required but length is zero")
+
+        div, mod = divmod(cls._size - len(blob), fill_length)
+        if mod != 0:
+            raise ValueError("invalid fill value, range to be filled must be multiple of fil size")
+
+        all_fill = fill * div
+        if align == "<":
+            return cls(blob + all_fill)
+        elif align == ">":
+            return cls(all_fill + blob)
+
+        raise ValueError(f"invalid alignment: {align!r}")
+
     def __str__(self) -> str:
         return self.hex()