For West System 5:1 ratio. 3 pump set for groups A, B or C. The pumps mount directly on the resin and hardener containers and eliminate the mess involved with measuring by weight or volume. WEST SYSTEM 300 Mini Pumps are calibrated to deliver the proper working ratio with one full pump stroke of resin for each one full pump stroke of hardener. The WEST SYSTEM 300 Mini Pumps Set contains one resin pump and two hardener pumps.