If it is both brake lights you really only have two culprits.
2. brake switch
Make sure you're checking the correct fuse. I can't remember how it is labeled, but I know it doesn't say "brake". I believe it is labeled "haz/stop" and on my YJ it is located in the upper right corner of the fuse box. It is a blue, 15A fuse.
If it is the brake light switch, you will find it underneath the brake pedal and is a pain to replace. You can check it a couple of ways. You can remove the connector and use a multimeter to check continuity, or you can check it by having someone place a multimeter on the brake light socket. One lead on ground, the other on the connection, (there are two so make sure you're on the right one. One for tail light with lights on and the other for brake light). It should show continuity when you have someone step on the brake pedal, and then show open when they release. If it shows open in both positions, and the fuse is good, then the switch is bad.
Make sure you don't have a bad fuse as a new switch is about 25 bucks or so.
To me, RC is kind of the Harbor Freight of springs. Sometimes you get a good deal and sometimes you don't.