They put these on late 113 series saws and 315 series Craftsman belt drive saws. These are an upgrade on the steel fences used on most 113 series saws. These will fit the best older 113 series saws if you want to upgrade. The 24/12 is for it has tape measurements on the rails for 24″ and 12″ on either side of the blade. It has one small mark where it looks like the blade touched it.