B&M 70239 Shift Improver Kit for Automatic Transmissions Recalibrates your automatic transmission for crisp shifts, optimum performance, and extended life Eliminates shift overlap and excess wear on clutches and bands due to slippage Two kits in one box -- select Stage 1 for RV/heavy duty applications, or Stage 2 for street/strip applications Installs easily with hand tools Backed by the manufacturer with a 1 year limited warranty