Check the listing for details. FIRENOCK Replacement Nocks J style for J3 lighted nock. Condition: New. Listed at 9.95 USD. Brand New Firenock replacement "J" style nock pack is the companion accessory for Firenock "J" style lighted nock. "J" style nock is specially designed (US pat.) to fit crossbow with short trigger box with an anti-dry-fire mechanism that cannot accept normal long nock prongs and with serving size of 0.155". "J" style nock can also be used as normal nock for standard carbon crossbow arrow with 0.300" ID. Features:Self-concentric systemCompression fit systemInstant release systemBest nock throat design for holding and releasingFirenock lighted nock system readyHigh precision molded with cavity number marked (e.g., J1 = J style nock, cavity 1)High quality German transparent plastic Contents: 7pc "J" style nocks in Red Notes: "J" style nock is designed to fit serving size of 0.155 +/-0.005".