Feature 【Strong Compatibility】The R0543200 rebuild part kit is compatible with all Polaris 3900 (P39) sport swimming pool cleaners models. 【Tune Up Rebulit Kit】The R0543200 tune up kit improves mechanical drive-train of the 3900 Sport cleaner. 【Features】The chain guard is used to ensure the drive chain is always aligned with the drive pulley. The tensioner and spring keeps the chain engaged with the sprocket for maximum torque transfer, and gearbox upgrades and built-in bearing guards. 【Superior Material】 The 3900 sport cleaner rebuild kit is made of quality material, treated with anti-corrosion and anti-wear, sturdy and durable. .