Size S is designed for lures measuring approximately 7.5 to 10 cm; size L is for 12.5 to 17.5 cm. The actual diameter of the body is the deciding factor: the ring must fit snugly without cutting into the material.
A Wacky Rigging Tool makes setup easier. Position the ring at the lure’s balance point, then slide the hook underneath. Packs of 25 are available in black or red to match the contrast of your rig.