These clevis allow you to quickly change blades when re-rigging. Simply snap them in and out effortlessly. The plastic system does not cut the line and the design makes changing blades quick and easy. Great for trolling spinners on monofilament. Troll are White, Casting Black in color. The Casting ,model has a barb end instead of a plain end on the upper frame, helps to hold the blade in the clevis better when casting.