diff --git a/pact_methodology/product_footprint/preceding_pf_ids.py b/pact_methodology/product_footprint/preceding_pf_ids.py
new file mode 100644
index 0000000..5c9b0e9
--- /dev/null
+++ b/pact_methodology/product_footprint/preceding_pf_ids.py
@@ -0,0 +1,45 @@
+from typing import List, Set
+from .id import ProductFootprintId
+
+class PrecedingPfIds:
+    def __init__(self, pf_ids: List[ProductFootprintId] = None):
+        """
+        A collection of preceding product footprint identifiers.
+
+        Attributes:
+            pf_ids (Set[ProductFootprintId]): The set of preceding product footprint identifiers.
+
+        Raises:
+            ValueError: If the provided list contains non-unique or invalid ProductFootprintId objects.
+        """
+        if pf_ids is None:
+            self.pf_ids = set()
+        else:
+            if not all(isinstance(pf_id, ProductFootprintId) for pf_id in pf_ids):
+                raise ValueError("All elements in pf_ids must be instances of ProductFootprintId")
+            if len(pf_ids) != len(set(pf_ids)):
+                raise ValueError("pf_ids must not contain duplicates")
+            self.pf_ids = set(pf_ids)
+
+    def add(self, pf_id: ProductFootprintId):
+        """
+        Add a new product footprint identifier to the collection.
+
+        Args:
+            pf_id (ProductFootprintId): The product footprint identifier to add.
+
+        Raises:
+            ValueError: If the provided product footprint identifier is not unique.
+        """
+        if pf_id in self.pf_ids:
+            raise ValueError("pf_id already exists in the collection")
+        self.pf_ids.add(pf_id)
+
+    def __iter__(self):
+        return iter(self.pf_ids)
+
+    def __len__(self):
+        return len(self.pf_ids)
+
+    def __repr__(self):
+        return f"PrecedingPfIds({list(self.pf_ids)})"
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diff --git a/tests/product_footprint/test_preceding_pf_ids.py b/tests/product_footprint/test_preceding_pf_ids.py
new file mode 100644
index 0000000..05f0465
--- /dev/null
+++ b/tests/product_footprint/test_preceding_pf_ids.py
@@ -0,0 +1,60 @@
+import pytest
+from pact_methodology.product_footprint.preceding_pf_ids import PrecedingPfIds
+from pact_methodology.product_footprint.id import ProductFootprintId
+
+def test_preceding_pf_ids_empty_initialization():
+    pf_ids = PrecedingPfIds()
+    assert len(pf_ids) == 0
+
+def test_preceding_pf_ids_initialization_with_valid_list():
+    pf_id1 = ProductFootprintId()
+    pf_id2 = ProductFootprintId()
+    pf_ids = PrecedingPfIds([pf_id1, pf_id2])
+    assert len(pf_ids) == 2
+    assert pf_id1 in pf_ids
+    assert pf_id2 in pf_ids
+
+def test_preceding_pf_ids_initialization_with_invalid_list():
+    with pytest.raises(ValueError, match="All elements in pf_ids must be instances of ProductFootprintId"):
+        PrecedingPfIds([ProductFootprintId(), "invalid_id"])
+
+def test_preceding_pf_ids_initialization_with_duplicates():
+    pf_id = ProductFootprintId()
+    with pytest.raises(ValueError, match="pf_ids must not contain duplicates"):
+        PrecedingPfIds([pf_id, pf_id])
+
+def test_preceding_pf_ids_add_method():
+    pf_id1 = ProductFootprintId()
+    pf_id2 = ProductFootprintId()
+    pf_ids = PrecedingPfIds([pf_id1])
+    pf_ids.add(pf_id2)
+    assert len(pf_ids) == 2
+    assert pf_id1 in pf_ids
+    assert pf_id2 in pf_ids
+
+def test_preceding_pf_ids_add_duplicate_method():
+    pf_id = ProductFootprintId()
+    pf_ids = PrecedingPfIds([pf_id])
+    with pytest.raises(ValueError, match="pf_id already exists in the collection"):
+        pf_ids.add(pf_id)
+
+def test_preceding_pf_ids_iter():
+    pf_id1 = ProductFootprintId()
+    pf_id2 = ProductFootprintId()
+    pf_ids = PrecedingPfIds([pf_id1, pf_id2])
+    iter_pf_ids = list(pf_ids)
+    assert len(iter_pf_ids) == 2
+    assert pf_id1 in iter_pf_ids
+    assert pf_id2 in iter_pf_ids
+
+def test_preceding_pf_ids_len():
+    pf_id1 = ProductFootprintId()
+    pf_id2 = ProductFootprintId()
+    pf_ids = PrecedingPfIds([pf_id1, pf_id2])
+    assert len(pf_ids) == 2
+
+def test_preceding_pf_ids_repr():
+    pf_id1 = ProductFootprintId()
+    pf_id2 = ProductFootprintId()
+    pf_ids = PrecedingPfIds([pf_id1, pf_id2])
+    assert repr(pf_ids) == f"PrecedingPfIds([{pf_id1!r}, {pf_id2!r}])"
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