Bohning's H.E. Nock fits reduced size shafts with an ID of .231" (commonly known as 6mm or H Nock) shafts. The H.E. Nock features a double-lock throat and a recessed index. Its throat size is .120" (3.05mm) and each H.E. Nock weighs an average of 8.0 grains (518.4 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.