These locking bracelets/anklets have a one sided screw that does not go all the way through like our previous designs. This enables the screw to tighten down. Size: All sizes are listed by Inside Circumference Weight: 3.3 oz (per cuff) Finish: Polished Stainless Steel Lock: 1 Position Key: Allen Style, Screw Shut - Our anklets are locked in place using a sunken screw with a tongue-in groove enclosure To measure: Wrap a flexible tape measure around you ankle above the ankle bone. Start by adding 1/4 to 1/2". Flex your foot to make sure the cuff wont bind. Most wearers usually say about 1/2" larger than your ankle measurement will be most comfortable.