diff --git a/src/ivfbuild.c b/src/ivfbuild.c
index 8a7b52d..cfff09d 100644
--- a/src/ivfbuild.c
+++ b/src/ivfbuild.c
@@ -365,8 +365,7 @@ InitBuildState(IvfflatBuildState * buildstate, Relation heap, Relation index, In
 
 	buildstate->slot = MakeSingleTupleTableSlot(buildstate->tupdesc, &TTSOpsVirtual);
 
-	/* TODO Fix item size */
-	buildstate->centers = VectorArrayInit(buildstate->lists, buildstate->dimensions, VECTOR_SIZE(buildstate->dimensions));
+	buildstate->centers = VectorArrayInit(buildstate->lists, buildstate->dimensions, buildstate->typeInfo->itemSize(buildstate->dimensions));
 	buildstate->listInfo = palloc(sizeof(ListInfo) * buildstate->lists);
 
 	buildstate->tmpCtx = AllocSetContextCreate(CurrentMemoryContext,
diff --git a/src/ivfflat.h b/src/ivfflat.h
index dd96f57..d3fa219 100644
--- a/src/ivfflat.h
+++ b/src/ivfflat.h
@@ -153,6 +153,7 @@ typedef struct IvfflatTypeInfo
 {
 	int			maxDimensions;
 	Datum		(*normalize) (PG_FUNCTION_ARGS);
+	Size		(*itemSize) (int dimensions);
 	void		(*updateCenter) (Pointer v, int dimensions, float *x);
 	void		(*sumCenter) (Pointer v, float *x);
 }			IvfflatTypeInfo;
diff --git a/src/ivfutils.c b/src/ivfutils.c
index 6ecf85a..74a4159 100644
--- a/src/ivfutils.c
+++ b/src/ivfutils.c
@@ -229,6 +229,24 @@ PGDLLEXPORT Datum l2_normalize(PG_FUNCTION_ARGS);
 PGDLLEXPORT Datum halfvec_l2_normalize(PG_FUNCTION_ARGS);
 PGDLLEXPORT Datum sparsevec_l2_normalize(PG_FUNCTION_ARGS);
 
+static Size
+VectorItemSize(int dimensions)
+{
+	return VECTOR_SIZE(dimensions);
+}
+
+static Size
+HalfvecItemSize(int dimensions)
+{
+	return HALFVEC_SIZE(dimensions);
+}
+
+static Size
+BitItemSize(int dimensions)
+{
+	return VARBITTOTALLEN(dimensions);
+}
+
 static void
 VectorUpdateCenter(Pointer v, int dimensions, float *x)
 {
@@ -309,6 +327,7 @@ IvfflatGetTypeInfo(Relation index)
 		static const IvfflatTypeInfo typeInfo = {
 			.maxDimensions = IVFFLAT_MAX_DIM,
 			.normalize = l2_normalize,
+			.itemSize = VectorItemSize,
 			.updateCenter = VectorUpdateCenter,
 			.sumCenter = VectorSumCenter
 		};
@@ -326,6 +345,7 @@ ivfflat_halfvec_support(PG_FUNCTION_ARGS)
 	static const IvfflatTypeInfo typeInfo = {
 		.maxDimensions = IVFFLAT_MAX_DIM * 2,
 		.normalize = halfvec_l2_normalize,
+		.itemSize = HalfvecItemSize,
 		.updateCenter = HalfvecUpdateCenter,
 		.sumCenter = HalfvecSumCenter
 	};
@@ -340,6 +360,7 @@ ivfflat_bit_support(PG_FUNCTION_ARGS)
 	static const IvfflatTypeInfo typeInfo = {
 		.maxDimensions = IVFFLAT_MAX_DIM * 32,
 		.normalize = NULL,
+		.itemSize = BitItemSize,
 		.updateCenter = BitUpdateCenter,
 		.sumCenter = BitSumCenter
 	};