Inception Designs Delrin Sled SC Harness or combined with the VisionTM 210000006466 or combined with the VisionTM anti chop system as an electro Precision machined from aircraft grade aluminum and then anodized with Type III anodizing – harder than normal anodizing this helps the bolt system resist scratches from dirt and debris They come with built in "slot blocker" to prevent dirt and debris from getting into the hammer area and reducing performance If needed the "Slot blocker" can be removed with simple tools to make a shorter sled for guns that don't have the slot extended all the way out the back of the body (like an Inception Bobtail Mid Block body)