300 Mini Pumps are designed for convenient and accurate metering of all Group Size A, B and C WEST SYSTEM resin and hardeners. They mount directly on the resin and hardener containers and eliminate the mess involved with measuring by weight or volume. 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 300 Mini Pumps Set contains one resin pump and two hardener pumps. 105/205-206 pumps deliver approximately 0.8 fl oz of resin/hardener with one full stroke of each pump. 105/207-209 pumps deliver approximately 0.9 fl oz of resin/hardener with one full stroke of each pump. As packaged, the pumps are ready to install on the Group Size B containers. A package of extension tubes for Group Size A containers is included with the set. Group Size C extension tubes are included in the 105-C Resin and in the 207-SC or 209-SC packages. If necessary, you can combine different group sized-as long as all of the pumps have a yellow head. To avoid confusion and possible off-ratio metering, 300 Mini Pumps have yellow heads, which should not be used in with any older pumps with a white head (301 and 303 pumps). Made of durable polypropylene, the pumps give years of dependable service. Read and follow the priming, ratio verification and operating instructions that come with the pumps.