The latches on your top and hardtop rely on this little doodad in order to stay closed. If it's worn, you'll find that the latch has trouble staying latched or is very easy to open, even if you've adjusted the tension. Replacing the lock cap is the solution.
You will have to remove the latch from the top in order to replace this. They are attached with thread locker and may be difficult to remove. Sold individually, you will need one cap for each latch you want to restore.
The design of this part changed in November 2002. The early one has a rounded point, the late one has a squared off end. We believe the VIN for the change is 2003 models ending in 021101, but please visually inspect your car to be sure. This is the early version. The later version is no longer available.
Mazda part NA01-R1-311.