These are special spacers (Part #0350) for use with Air Bags for tuning the rear suspension. They are 1" thick with a hole in the center for the fill line to go through. The material is a special high density, wear and abrasion resistant plastic, that holds up to high temperatures also. They are designed to be installed under your current air bags and thin spacer/discs, against the rearend housing. There are 2 pieces to a kit, one for each side of the car.
The spacers allow less air pressure to be used in the air bags, and still give the same amount of down-force. This reduces/eliminates that initial all familiar bounce from the rear which unloads the chassis. This bounce is the main cause of why a car launches initially with good traction, but spins just after it starts moving, and then hooks up again (hopefully). It is amazing how a little thing like these spacers can dramatically improve traction and lower the 60 ft times on many cars. These are recommended for anyone running more than approx. 15 psi in any bag. The spacers allow the same or more down-force, without turning the air bags into basketballs. These were proven to lower the 1/4 mile time of one car at the 2001 Buick Nat's by over 2 tenths. This will obviously vary from car to car, but they do work great on every car so far.These are extremely helpful in the 1.4 to 1.7 60 ft. range, and will be a good addition to cars in other ranges as well. Air bag pressure tuning suggestions and recommendations are also included with each kit.