I don't think he's asking for how anti-cant indicator works. He's asking why would he need a 20 MOA base when a Vortex Razor has a total elevation adjustment of 125 MOA. Cant is also used in describing the angular relationship of how the scope is mounted in relation to the barrel ... On either case, it's best not to hijack this thread. My sincere apologies to Lievois if I strayed you off course. Cheers!