Petrol Throttle - Gunmetal with Machine Face and Stainless Steel Lip One of the newest additions to the Petrol single-piece line of wheels is the Throttle. The Throttle features a classic five spoke machined face with machined accents and a stainless steel lip with added rivets. By inserting a stainless steel lip Petrol achieves the visual effect of a multi-piece wheel while maintaining the simplicity of a one piece wheel. Stainless steel lip wheels have been a breakthrough in the one piece wheel design. Available in 18", 19" and 20" diameters.