Dual 62/70mm RBC adaptor has a unique press fit 7.5mm ring that allows the use of either a stock 62.5mm RSX throttle body or a larger aftermarket 70mm RSX flange unit.
If you decide to upgrade to a larger 70mm aftermarket throttlebody later on, simply press out the ring and install the adapter.
This kit comes complete with hardware for both 62.5mm and 70mm throttle bodies, so again it wil work if you decide to upgrade later on.
If you want to go back to stock for whatever reason, press the ring back in and install your oem RSX throttle body.