The Adjustable Nut goes on threaded 1″ rods/bolts, they come with many of our products but can be added to any threaded 1″ rod. Our Adjustable Nuts are machined out of a solid piece of Acetal plastic in Columbus Ohio, we chose Acetal plastic for its high tensile strength and low friction coefficient giving the nut high resistance to wear and abrasion protecting both the threads of the attachment and the upright.  Adjustable Nuts currently come with our Adjustable Landmine, Neck Attachment, Adjustable Weight Peg, Belt Squat Stop, and Alpha Single Roller.