My zapper was purchased from Essence Instruments. It differs from other zappers in that it zapps at 30,000hz and 2,500hz, choosen by a switch. The lower frequency is supposed to be better for parasite killing. In a ten minute session I would zap for 7m at 30,000hz and 3 at 2,500hz. There webby will tell u all about it. But you must also zapp correctly. Use copper handholds not rist straps. There larger surface area, keeps skin resistance down to the minimum, which is what u want, the least resistance possible. Means more of that healing energy traveling through you. U must also wrap the handholds in 1 or 2 layers at the most of paper towel, soaked in slightly salty water. This cuts the resistance down to about as low as u will get it. Dont over rap the handholds, especialy if only soaking in water, the resistance goes way up, and u wont get that healing energy through u. Also switch handholds round halway through a session after 5 mins or whatever. This will really help