If I really want a good mix of throw and spill in a true ‘pocket package’ a UF501A body plus an IMR 18350 with a very well driven XML Hi drop-in plus a decent copper shim around it for good heat transfer, seems to me the best and cheapest compromise. A decent 501A de-anodised always looks far better than when its in the black. Its always annoyed me that you can get 501B’s in every damn color or camouflage but you can’t get a 501A in anything but black. Who designed it, Henry Ford?