diff --git a/lib/hkStubs/Havok/Common/Base/Math/Vector/hkVector4fComparison.h b/lib/hkStubs/Havok/Common/Base/Math/Vector/hkVector4fComparison.h
index e180c961..1d824c6a 100644
--- a/lib/hkStubs/Havok/Common/Base/Math/Vector/hkVector4fComparison.h
+++ b/lib/hkStubs/Havok/Common/Base/Math/Vector/hkVector4fComparison.h
@@ -1,9 +1,66 @@
 #pragma once
 
-// FIXME: incomplete
+#include <Havok/Common/Base/Memory/Router/hkMemoryRouter.h>
+#include <Havok/Common/Base/Types/hkBaseDefs.h>
+#include <Havok/Common/Base/Types/hkBaseTypes.h>
+
+#ifdef __aarch64__
+#include <arm_neon.h>
+#define HK_VECTOR4F_AARCH64_NEON
+#endif
+
+using hkVector4fComparisonParameter = const class hkVector4fComparison&;
+
 class hkVector4fComparison {
 public:
     HK_DECLARE_CLASS_ALLOCATOR(hkVector4fComparison)
 
-    hkUint32 m_mask;
+    HK_FORCE_INLINE static hkVector4fComparison convert(const m128& x) { return {x}; }
+
+    HK_FORCE_INLINE void setAnd(hkVector4fComparisonParameter a, hkVector4fComparisonParameter b);
+    HK_FORCE_INLINE void setAndNot(hkVector4fComparisonParameter a,
+                                   hkVector4fComparisonParameter b);
+    HK_FORCE_INLINE void setXor(hkVector4fComparisonParameter a, hkVector4fComparisonParameter b);
+    HK_FORCE_INLINE void setOr(hkVector4fComparisonParameter a, hkVector4fComparisonParameter b);
+    HK_FORCE_INLINE void setNot(hkVector4fComparisonParameter a);
+
+    HK_FORCE_INLINE void setSelect(hkVector4fComparisonParameter comp,
+                                   hkVector4fComparisonParameter trueValue,
+                                   hkVector4fComparisonParameter falseValue);
+
+    m128u m_mask;
 };
+
+inline void hkVector4fComparison::setAnd(hkVector4fComparisonParameter a,
+                                         hkVector4fComparisonParameter b) {
+    m_mask = a.m_mask & b.m_mask;
+}
+
+inline void hkVector4fComparison::setAndNot(hkVector4fComparisonParameter a,
+                                            hkVector4fComparisonParameter b) {
+    m_mask = a.m_mask & ~b.m_mask;
+}
+
+inline void hkVector4fComparison::setXor(hkVector4fComparisonParameter a,
+                                         hkVector4fComparisonParameter b) {
+    m_mask = a.m_mask ^ b.m_mask;
+}
+
+inline void hkVector4fComparison::setOr(hkVector4fComparisonParameter a,
+                                        hkVector4fComparisonParameter b) {
+    m_mask = a.m_mask | b.m_mask;
+}
+
+inline void hkVector4fComparison::setNot(hkVector4fComparisonParameter a) {
+    m_mask = ~a.m_mask;
+}
+
+inline void hkVector4fComparison::setSelect(hkVector4fComparisonParameter comp,
+                                            hkVector4fComparisonParameter trueValue,
+                                            hkVector4fComparisonParameter falseValue) {
+#ifdef HK_VECTOR4F_AARCH64_NEON
+    m_mask = vbslq_u32(comp.m_mask, trueValue.m_mask, falseValue.m_mask);
+#else
+    m_mask = (comp.m_mask & trueValue.m_mask) | (comp.m_mask & ~falseValue.m_mask);
+#endif
+}
diff --git a/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h b/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h
index 71638a1d..8a6ef47c 100644
--- a/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h
+++ b/lib/hkStubs/Havok/Common/Base/Types/hkBaseTypes.h
@@ -28,6 +28,7 @@ using hkObjectIndex = hkUint16;
 using hkTime = hkReal;
 
 using m128 = __attribute((vector_size(16))) float;
+using m128u = __attribute((vector_size(16))) hkUint32;
 
 class hkHalf {
 public: