It depends - Geissele Super 42 Braided Wire Buffer Spring And Buffer Combo, H1 - Best Seller!

As most of you know gas tuning is part of the part of the art of ownership. For those without adjustable blocks you need to be careful. I bought this for a 18"Rise watchman 6mm arc and ran into trouble. I suspect the 18" barrel is not pushing enough gas to push the bolt fully back consistently. I've used Geissele in all my builds, works great in my 300blk 8" but (and no it was not the buffer weight) the spring is just a little heavy for low gased build. Its a great product but use caution based upon your gas system