Bore Adapter, 3/8'' Bore for 17mm Bearing, Steel, Designed to work with 17mm single-row heavy duty bearings, known as ''6203'' type, and will reduce your inside diameter to 3/8''

Back Side Offset: The width from the center of the pulley to the backside edge of the hub or bore adapter.

Fits with Bearing: The size of the bearing the bore adapter is designed to fit into. Phoenix bore adapters are available for 5/8" and 17mm bearings.

Frontside Offset: The width from the center of the product to the front edge of the hub, bearing, or bore adapter.

Inside Diameter: The distance across the center hole, or bore, of the product. This dimension should match the diameter of your shaft or bolt.

Material: Describes what the product is made from. Plastic, aluminum, and diecast are softer, lighter, and do not rust. Steel and cast iron are meant for heavy-duty applications, but can rust in certain circumstances.

Outside Diameter: The distance across the circle of the product, from outside edge to outside edge.

Shoulder Length: The size of the shoulder on the bore adapter. When assembled into a bearing, this is the distance from the edge of the bearing to the edge of the bore adapter. Some bore adapters do not have a shoulder length. These are known as "sleeves" because they match the width of the bearing.

Throughbore: Length of the bore, from one edge to the other. The Frontside Offset and Backside offset together equal the length of the throughbore.