Selling a pair of Gravely front suspension casters that fit on (Pro Turn) PT100, PT200 and PT400 series zero turn mowers that have a domed metal cap on the top of caster spindle shaft tube and when pried off with a screwdriver there is a castle nut with a cotter pin. The top of the spindle shaft is threaded where most other models had a bolt and internal threads. The shaft diameter is 1" and about 3-1/2" long. These were never mass produced so you can't order a pair anywhere. Suspension casters have a dampening puck and open & close like a clamshell to offer a much smoother ride as they are not Ridgid. Coupled with a good suspension or air ride seat, they handle bumpy terrain like a Cadillac. The  ones offered for more popular models are a $400 dollar optional accessory. These are not perfect cosmetic condition and may have scratches and minor imperfections but we're never used in the field. If you have a PT100,200 or 400 series Gravely mower, these will drastically improve ride quality and there is nowhere else you can find them. Let me know if you have any other questions and good luck bidding !