Double lock system nock that is designed for D loops. This nock is made to keep your arrow on the string during "let down". Insert style nock that will fit either Standard Carbon Shafts or Easton CB Uni-bushing and G-nock system as well as standard carbon shafts that weigh is 6 grains or Easton Axis and smaller diameter style system that weigh is 7 grains. Dozen pack. Available in three sizes. Size: Std carbon Color: Neon Org Size: Std carbon