It's all about choice! Since we make them in house, we can be more accommodating...
We have them available for Harley or Triumph/British
Choice of flat, domed or finned ends.
Choice of finish - raw, black powdercoat, or polished.
Choice of push in cap, or screw in cap.
We also make our caps (aluminum or brass faucet style) and bungs (aluminum, or steel) so that people can use them in their own custom gas or oil tanks. See our full line up at http://choppahead.com/.