These are diffusers that fit the fully printed flashlight. Replace the original bulb conductor with this threaded one, then pick your diffuser and screw it on.

I have found it most usable to actually glue the diffuser to the bulb conductor after the bulb is installed. It does mean you have to have a separate led for each diffuser, but the led will last long enough to not worry about burnout, and it makes the diffuser much easier to use to turn the flashlight on and off.