Lemme guess...you want to swap out the yellow and install the red one in the one you just got from me? Hehehe...
I posted that same question a while back - from what I recall, you have to insert needle nose pliers into the two holes in the red retainer ring and unscrew the assembly. I'm sure someone else will chime in.
There's a recent post about the Jet 1 Pro that has pictures on how to take the tailcap apart.
A pair of tweezers with long, narrow points would work best. Pinch both openings on the ring around the spring and rotate cap or tweezers. Once it comes off the pieces below can be pulled up or dropped out if you flip the tailcap over. A decently sized paper clip might do the same trick.
Wicho, I love it! I got the sickness bad.... In the two weeks I've been a member I've bought your cle, a cheap DE light, and have a jet 1 pro and a fenix t1 on the way....
Thanks for the info I'll try the tweezers thing tonight.