These clasps work by letting you hook the leather onto itself. In a nutshell - take a piece of leather double the length of the finished bracelet, and fold in half. Slide a bead of your choice over the two ends and push down towards the centre. Insert the two cut ends into the hollow, open end of the clasp, and glue into place. The New Super Glue or any gel cyanoacrylate will work well. When dry, push the loop formed at the center of the leather through the hole, and hook onto the hook. The bead you added initially stops the stiff-ish leather from opening up too much. Super easy once you know how. Hole is 5 x 9.8 mm
22mm By the each.