Developed in 2015 this precision machined 6061 aluminum adapter allows RX7 owners to replace their dated telescoping radio antenna with a modern stubby / S2000 antenna
The adapter itself was painstakingly designed to properly connect to the stock internal Mazda antenna connections inside the base unit while insulating the adapter from the chassis ground. The result is a low loss bridge between the RX7 headunit and the new stubby antenna of choice.
This kit works by utilizing the stock 93-95 RX7 antenna base unit. Consequently, you'll need a stock antenna base unit along with all the parts it uses to make its exit out of the passenger rear quarter panel. If your grommet and locking retainer / nut haven't aged well simply due to the fact that it forms the external section of the stock antenna, you can order new ones using the Mazda part # FD01-66-A9Y. This is the part number for both the grommet and the locking retainer/nut.
You'll also want to purchase a compatible antenna to use with the adapter. This adapter was designed to work with OEM Honda S2000 antenna which is part number 39151-S2H-E01. You can easily google this part number and find a dozen dealers that will happily sell you one for ~$25 shipped. Alternatively, there are plenty of aftermarket solutions. As long as you can get one that's threaded for M5x0.8 (most are) it should fit very well.
See the installation tutorial here