the 400ex, 450r and yfz 450 shock all require some modification to install. The 400ex and yfz450 seem to require about the same amount, since the mounts on both need to be modified to fit the blaster correctly. There used to be a DIY on the 400ex shock mod but i can't find it now. There is still a good amount of info on mounting each shock, you just have to search a little.