Chinesium sub-par buffer - Dark Storm Industries DS-15 H2 Carbine Length Buffer 4.5 oz

Started getting wear on the face from the spring after less than 100 rounds, so probably softer aluminum - not mil spec. They put oil inside because they use poor quality steel weights, which sticks the rubber spaces to the weights and makes it act like one big steel weight and so your deadblow dies. Buy once, cry once. Stay away from this buffer.