These kits fit Invader chassis specifically, which is 1 1/8" OD tube, with 0.970" ID. This translates to 28.6mm OD, and 25.6 mm ID.
Assists in the mounting of the rear bumper, fits within the rear frame tubing with expandable cinch bolt / rubber bushing that fits tightly against inner wall of tube to prevent loss of bumper during racing conditions.
Each bolt kit includes: large lag bolt, internal rubber bushing (expands within frame), milled spacers for fitment to chassis tubing and bumper support upright, and associated retainer and cinch nuts (outward facing).
**NOTE** Each bolt kit is sold individually, meaning for all applications (2) kits are necessary to properly mount a kart bumper. Each kit does not come with the uprights or bumper supports.