18-pack. Shim kit includes 6 of each .010"; .005" and .003" thickness. Used to quiet your engine and reduce wear by reducing end play of rocker arm to cylinder head. Feuling recommends 0.0035" to 0.0045" for optimum rocker arm oil psi and noise reduction. M8 cylinder heads also have excessive wear on the rocker arm standoff trusting surfaces; when the hardened shim is placed on the thrusting side it will assist in reducing further wear and damage to cylinder head. Will benefit stock engines and highly recommended for engines with high lift camshafts or higher pressure valve springs. Note: Shims should be installed by a professional; one who can make correct end play measurements and can install and tighten rocker shaft nuts/bolts without damaging shims. USA made.