What size feet are you ? If your an 8 or above then you'll need the large cinch. I have a pair of med cinch and i'm a size 8 but i use Airwalk boots which have a smaller profile than most boots. I can't use my Burtons in the them cos their profile is to big ! Hope this helps
my wife uses cinch bindings large ones, and she wears northwave boa boots size 8. These boots have a large profile but aren't a problem in the cinch bindings. myself I also use cinch bindings with 32 306 boots size 9 again size large bindings, not a problem fitting the boots in. In both cases the straps have plenty of adjustment.