bootsole length is on the side of the heal your boot it will be in millametres, just put your boot in the binding there should be alittle line near the arch on the lower side of your boot, measure how much more forward you are then the mid sole line on the ski. if the little line on your boot is 3 cm's infrontof the midsole line on the ski, you are mounted at +3 from midsole, you dig