Aluminum Washers 1- Thickness- The washers are 0.200″ thick for optimal strength. 2- Dimensions  -The washer inside diameter is 5/16″. The outside diameters is 1.175″ . 3- Original ACS washer – The BEST on the market today! 4- Minimum weight. Maximum strength. 5- Made of a high strength aluminum alloy. 6- Back side is counter-bored to insure a flat, snug fit against the track. 7- Machined, not stamped, keeping material strength at its best.