Designed For Drag Racing Only. Pro Gears may be necessary when tooth breakage occurs with Standard gear sets. Produced from a softer material, the teeth can flex as opposed to crack and break. The life expectancy can vary anywhere from 15 to 300 runs depending on the vehicle. If a Standard gear provided acceptable life, a Pro gear may not be the right choice. Machined From 9310 Forged Steel. Heat Treated to Optimize Material Properties.