The discs are replacement components found in the all64320 bump stop kit, along with other durometer ratings for even more fine-tuning. The 2.10 OD discs have a 5/8 ID hole suitable for 0.630 in shocks, as well as many other uses, including suspension limiters. Features: Place inside the bump stop stack to limit travel. The 2 OD shims work with most 0.630 in shocks. The kit makes it easy to start using bump stops. It includes a selection of 20 shock bump stop discs ranging from 50 to 75 durometers, 8 backup washers, and 16 packing shims in a simple plastic carrying case. Specifications: Color: Black. Thickness: 0.06. Size: 0.630 in