The aeration cap option will give your shocks a slightly softer feel, similar to reducing the oil viscosity. When using these caps, you will want to use #100-150 heavier shock oil to achieve the same feel as your standard setup. The caps will provide an advantage in bumpy conditions by allowing the car to more efficiently soak up bumpy track sections and they help provide more grip on loose surfaces. Plus, they will allow the car to settle more quickly when landing large jumps. Package includes instructions, four caps, four o-rings and all necessary hardware.