The PROTO Full Knuckle SCS™ is the original and first Standard Compression System. It fundamentally changed the way a freestyle scooter was built and effectively revolutionized the freestyle scooter after market parts industry. The Full Knuckle SCS™ is still the strongest and most universally compatible SCS™ ever created. The Full Knuckle SCS is built to perform and last and carries a lifetime warranty on cracking. Made of High Grade 6061-T6 Aluminum. Includes Compression Washer and 5 Bolts. For use with Standard or Oversized Bars. 100% made in San Diego, California.