Horrible "TENS" unit if that's what you're looking for
I purchased this Machine for $12 and thought I was going to get something good for a quarter of the price. I'm Athletic Trainer and I also work in a physical therapy clinic and I know how a tens unit should feel. This machine doesn't let you choose your comfort level. I think there's 10 levels of strength and I can only get to about level 4 before the machine starts hurting like hell! I like TENS units with a adjustable know that can change the frequency. This machine goes from one level to the next too quickly which is painful. I did not enjoy this machine at all.