Most commonly used on injected blown gas, alcohol or nitro applications. Typically a fuel shut off will include AN fittings to the size of the shut off. So if it is a -12 shut off it will have -12 AN fitings but the customer can specify different size fittings at no additioanl cost.
Customer can choose -6 return line if they choose and is shown in pictures as an option. Racer can pick shut off size from drop down menu.