It is a black plastic Colt buffer they use on their A2 stock civilian models. They do not hold up and most in the know chuck them for a Mil-Spec buffer. This is the drunken uncle at a family reunion issue that many of the Colt flag wavers do not talk about when Colt cheapens here and there on the Civilian rifle sales. I hade one in a Match Target I bought new in 1999. Do not know if Colt still uses these or not.