3/8 Inch Stud Compatibility – Designed for use with 3/8" rocker arm studs, making these poly locks ideal for stock-style rocker arm applications Sure Lock Fastening Design – Special heat-treated and plated sure-lock nuts help maintain consistent valve adjustment under demanding conditions Complete Set of 16 – Includes sixteen poly lock nuts to service a full engine valvetrain setup Included Allen Wrench – Supplied with an Allen wrench for straightforward installation and adjustment Durable Construction – Features a 5/8" hex, 1.10" overall height, and .600" outside diameter for a secure fit and long-term reliability These Poly Lock 3/8" Set of special heat treated and plated 3/8" thread sure-lock nuts are supplied with an allen wrench. Set of 16. 5/8" Hex. For use with stock style rocker arms. .600 Diameter.