This is a Datsun 510 Idler arm WITH the Delrin bushing kit already installed. This kit incorporates a thrust washer for pre-load. It eliminates the drag and binding that you find with other kits. This kit is made from Delrin material and a stainless steel sleeve. When you purchase this kit you will receive a new idler arm with the bushing kit already installed save your time and labor! Let us do it for you.