I know that this is kind of old news, but I am adding for completeness. I cannot fathom the purpose of this device. From the manufacturers website:

A LaserLyte original, the Pistol Bayonet is ready for any situation – or just looking cool on your favorite gun.

I can’t think of a situation where I need this, nor one where it would look cool. Some people have made the “weapons retention” argument, but I remain unconvinced. This is about as useful as a fish bicycle.