These clutch baskets are CNC machined from billet aluminum and patented replaceable stainless steel inserts are attached to prevent severe "grooving" of the basket where the clutch plate tabs make contact. Oil passage windows are also machined into the basket to increase oil flow to the clutch plates resulting in cooler operating temperatures and longer clutch life. The end result is an incredibly durable clutch basket and, quite possibly, the last basket you will ever need to buy for your motorcycle.