A set of three pumps: one for resin, two for hardeners.  It is amazing how much mess you can avoid by using these!  They fit right onto the containers of West System resin and hardeners and are pre-measured to deliver the correct amount of substance per full pump stroke.  One full pump of resin is the right amount to mix with one full pump of hardener.  Simple to use and we highly recommend them as they are what we use in the store.