I find the brass and Delrin tips most useful, I use the brass tip to strike punches as it will not cause the head of the punch to mushroom. I use the Delrin for the last tap to seat a pin, that way if you slip there's no damage. If you use the steel punch and slip when administering that last tap, you'll leave a nasty mark. I seldom use a steel hammer, mostly for peening rivets. Aluminum will leave a nasty mark on blued gun steel, one that is near impossible to remove. As a Gunsmith/Toolmaker, I've made my own small hammers for years, Shooboy's are real works of art though. Another hint I might add is that if you can find some bronze, it makes better hammer faces than brass. Brass will mushroom and the mushroomed protions will break off and are a danger, bronze will deform with use but will not mushroom and shatter. A really good material which is tougher than Delrin is VektonPB, it is used for pile driver faces and is incredible tough yet non-marring like Delrin. In addition to hammer faces, VektonPB makes great bench blocks. Anyone interested in a source for VektonPB is welcome to contact me at my e-mail address.