The Dead Air Shim Kit for barrels with 1/2-28 or 5/8-24 threads is composed of three different shim thicknesses. The graphic on the packaging details the thicknesses and identifying features of the shims included with the kit. Always place the thickest shim(s) on the barrel first. SPECIFICATIONS: 1/2-28 One notch - Qty 4, .004a ^2 thick, ~40 degree rotation, ~1/9 turn Two notches - Qty 5, .006a ^2 thick, ~60 degree rotation, ~1/6 turn No notch - Qty 1, .060a ^2 thick, ~1.7 turn 5/8-24 One notch - Qty 4, .004a ^2 thick, ~35 degree rotation, ~1/10 turn Two notches - Qty 5, .006a ^2 thick, ~50 degre Mfg: Dead Air Armament