-12 AN Yamaha Thermostat Housing mounts to your Yamaha R6 engine similar to how a stock thermostat housing would, but instead of using a regular push-on rubber hose it features a -12AN fitting to allow you to use braided or PTFE hose with a fitting. This will provide a more secure fit, reducing the chance of leaks or worse. Fits 1999 and newer Yamaha R6 engines.