three is good. I don't even want to know what level ...
This gift was for my wife, and she loves using it after a long day of work. For her, level two is strong enough. For me, three is good. I don't even want to know what level 4 and 5 feels like. I'm pretty sure the heater is not very strong, but that's not important. I'll update this if anything goes wrong.
Rating: 5 stars