Aeroski Springs Kit 2.0 Experience maximum durability and customize user resistance with RSR (Recoil Spring Resistance), exclusively compatible with Aeroski 2.0 (Not compatible with Aeroski 3.0)Includes:2 springs (Length 5.9 inches) 2 O-rings*Aeroski can use a maximum of 4 springs simultaneously.Please check your manual to make sure which version of springs you need before ordering. Don’t know which springs you need? Please reach out to our customer service team at [email protected] and we will be happy to help you choose the right part.