They take a little getting used to. I had given mine up for awhile, but am back to carrying it some now... it suddenly seems to be working for me.
The trick is, when you punch to hit with both the prong and the outside of the index finger ring. Otherwise, punching with just the prong, will hurt your wrist some.
They are great for hammer fists and reverse hammer fists. This is primarily how I use one, but I do normal punching with it too.
For a carriable impact weapon I actually do prefer a
Comtech Stinger or a palm stick with a finger loop called a
Koppo Stick, but the DTL Impact Kerambit is also pretty decent.
The one I am wanting right now is the
Laci Szabo Silat Hook/Crook Hook (AKA The Water-Lilly Massager). Its sold as a massage tool (and weapon), works as a massage tool... looks harmless to the untrained eye... and it would seem to pack a hell of a punch, an Impact Kerambit, Stinger, Koppo and Crook Top cane all rolled into one... looks like a fistful of mayhem making and meat mangling potential.
Enjoy your DTL, they are fun, and do work rather well once you get used to them. I think there are better options, the Stinger and Koppo, because they are more natural to use and dont require "getting used to", and they do more, for me at least... but the DTL Impact Keram is still something I carry often enough to say I depend on it.