The KAK Configurable AR-15 Carbine Buffer Kit 9mm allows you to configure and tune your buffer for your AR-15 build. Using different combinations of the supplied parts, weight combinations of up to 10 oz are possible. The modular kit is great for finicky 9mm builds, full auto fire, and subsonic loads. Includes 1x 9mm Extended Steel Buffer Body, 4x Aluminum Weights, 4x Steel Weights (Black Oxide Coated), 4x Tungsten Weights, 4x Rubber Spacer Disks (1 spare).