Blaster shock mounts require a larger 12mm bolt. Both top and bottom holes on the frame are 12mm. The 400ex shock has 10mm bolt holes. Therefore there is alot of slop in the shock mounts. The bushings that go in the top frame mount have a outside diamete of 12mm and a inside diameter of 10mm. You then run a 10mm bolt through the bushings and the new shock. On the bottom of the shock you drill out the 10mm hole to a 12mm. The bottom of the shock does not have a bearing so this is why your able to drill through the shock.