Once you remove the stock lid and the fuel nozzle cap with unscrewing four bolts hold it in place - don't forget to cover the fuel nozzle otherwise you'll have a terrible headache after the installation due to the fuel fume. :) The kit consists of a large cast alloy bowl that fits into the existing fuel lid area and hold there using supplied stainless steel four screws and fuel nozzle cap. Oh by the way it's important to screw the hinge and push back the fuel lid release hook before you put this bowl. Once the bowl is in place push back the release hook and tighten up. The fuel lid supplied is Monza style cast alloy. It's quite heavy and you can polished it up if you want with the supplied polish compound. With the spring plate, screw the fuel lid to the hinge using the included chrome Allen screw.
The beauty of this fuel lid is it can be locked and be used with the stock fuel lid release lever. The PBC's racing fuel lid, however, is unlockable. In modern society you never know when some crook will put some sugar or sand into your fuel tank. :( Also they can steal your fuel since anyone can open it. :) The best part is this kit costs just over 10,000yen which is a bit over A$100 at current exchange rate. Compared to the PBC lid that quoted at over U$350 plus import duty and sales tax that's almost a bargain!
After yearning for that flip-top racing fuel lid on the V8 Monster Miata, I found this replacement lid. It's made by Autoblaze - in case you're wondering this is the company making that chrome windshield cover - and replaces entire stock fuel lid assembly. It's very easy to remove the stock fuel lid -all you need is unscrew the two bolts hold the fuel lid hinge assembly.