*** All Beiter Nocks require a .113-.114" Center Serving Diameter for maximum performance *** * Except for #1 Small groove which requires .102-.103" * - For Recurve and Barebow use only Whether you are a seasoned hunter, aspiring professional or anywhere in between - Beiter nocks are designed with you in mind! All Beiter nocks are precision molded within 0.2mm tolerance (1/125") under the strictest German engineering and manufacturing principles. On the competition scene, Beiter nocks have won more medals than any other nock in history - and they are quickly becoming a popular choice among hunters and TAC shooters who demand the utmost performance and quality when they stress their equipment to the max. When selecting your Beiter Nocks, please use the following guide for sizing: Altra: Centrum .166 = 166 Centrum .246 = 19/2 Novum .204 = 204 Black Eagle: Deep Impact, X Impact = 165 Rampage, Spartan = 204 Gold Tip: Hunter (Regular, XT, and Pro), Ted Nugent, Velocity, Force = 19/2 Airstrike, Kinetic (KAOS), Quantum = 204 Pierce = 166 Easton: 6.5mm shaft or S bushing= 19/2 5mm shaft or X bushing = 204 4mm shaft or G bushing = 166 UltraView Ultraview 1K = 166 Victory: RIP XV = 204 VAP = 166