Bohning's Blazer® Nock fits standard carbon shafts with an ID of .246" (6.25mm, but commonly known as 6.5mm) and Super UNI Bushing systems. The Blazer® Nock features a double-lock throat and a raised index. Its throat size is .120" (3.05mm) and each Blazer® Nock weighs an average of 9.0 grains (583.2 mg). Tech tip: for easier insertion and indexing, apply a small amount of Bohning's Tex-Tite or Seal-Tite Wax to the nock shank. NOT ALL BRANDS OF NOCKS ARE CREATED EQUAL At Bohning, every nock style must pass the following steps before introduction to the market: 1. Computer simulations identify potential weak points. 2. Destructive testing methods expose possible design flaws or material defects. 3. Accelerated life cycle testing using a custom-built bow is performed at kinetic energy levels exceeding 110 ft-lbs (nearly twice that of most hunting bows). A single nock must withstand over 1000 shots or it goes back to step 1. Proudly manufactured at the Bohning Factory in Lake City, Michigan, United States.