As I get older and with a dodgy back I'm always looking for rabbits to 'pull out of a hat' in order to keep me upright. With the annual onset of the cold I can get lower back muscles spasms that can get quite serious. This solves it. I put it on before heading out in the morning and just have it on for say the first hour until I'm happy that I've warmed up doing the physical work I need to do. The vibration feature can be handy at the end of the day but when on with heat will chew the battery up fairly quickly. I purchased with the 10,000k mAh battery but have added a quite large (and heavy) 20,000 mAh one, it just fits in the belt battery pocket.
Quality is excellent, and it comes with a spare fly lead, (they do flex and break eventually, all brands)