SCS 10-Spline Quick Change Gears, Sets #1 thru #30K, with the exception of 15K, are Max Lightened, where possible, without sacrificing the strength! Average weight savings 1 ½ lbs.! Since 1987, SCS Gears have been the proven leader in Ultra High Performance Quick Change Gearing. SCS builds gears that Last! SCS Gears are made of 9310 Aircraft Alloy for maximum strength. Each gear is Crown Shaved (Ground before Heat Treat) to minimize backlash and run out, broached for proper 10-spine shaft fit and Black Oxide finished. The SCS Extra 5 step heat treating process yields maximum gear life for high stress applications such as Big Block Oswego Super Modifieds, World of Outlaw Sprint Cars and IROC Series Cars