BBR Tuning PRO Series 2Stroke/4Stroke Motorized Bicycle Performance Spring Idler Pulley &ndash; Gas Bike Chain Idler Pulley Upgrade NO ADJUSTMENTS NEEDED: The BBR Tuning Pro Series Performance Spring Idler Pulley features a heavy duty spring to keep constant chain tension. No longer do you have to keep adjusting your idler to compensate for your chain stretching out. HEAVY DUTY DUAL SUPPORT: With dual rollers your chain is locked in place offering better alignment and constant tension. The bracket is thicker steel and a more sturdy design so that your chain is less stressed and can drastically extend the life of your chain. EASY INSTALATION: Just unbolt and remove your older idler pulley and bolt your new. No adjusting tension as the spring will keep it perfectly adjusted every time. UNIVERSAL FIT: Compatible with 415 heavy duty bicycle engine chains, regular and spring chain tensioner. Works for both 2 stroke and 4 stroke motorized bicycle engines and most standard city bikes, cruisers bikes, beach cruisers, mountain bikes and road bikes. INCLUDED COMPONENTS: 1x BBR Tuning PRO Series Spring Idler Pulley, 1x Mounting Hardware