For greater durability and consistent performance in the Powerglide TCI has created the Dual Ring Servo Kit which receives hydraulic oil in order to tighten the bands around the transmission drum to prevent it from turning. This kit uses two Teflon sealing rings in place of the original single design or dual rubber ring designs offered elsewhere. This doubles sealing effectiveness and prevents excessive leakage which can reduce band apply force. This feature also reduces vehicle rocking when the transbrake is applied and provides additional stability in low gear. Perfect for the Super Class racer seeking positive transbrake engagement when staging.