Specially designed for convenient and accurate dispensing of WEST SYSTEM 105 Resin and 205 or 206 Hardeners. The pumps mount directly on the resin and hardener containers and have been calibrated to deliver the correct working ratio of 5 parts by volume of resin to 1 part by volume of hardener with one stroke from each pump. WARNING: DO NOT USE 301 MINI PUMPS WITH 207 OR 209 HARDENERS. Use the 301A set (5:1 by volume) to fit the A Pack size