BD ANATOMIC INSOLES Features Heat-moldable, anatomically shaped insoles with preinstalled Hotronic heating elements Designed for use with Hotronic S4 Footwarmer Power Kit (sold separately) Trim to fit Imported. Sizing information based on shoe size: Small fits Men's 5 6 and Women's 6-7 Medium fits Men's 7-8 and Women's 8-9 Large fits Men's 9-10 and Women's 10-11 X Large fits Men's 11-12 and Women's 12-13