Great unit, powerful, pounding but... first time use after charging it lasted only 10 min and died. Realized the charger I used ( charger not included with purchase) was a 5V/1A and not the 5V/2A as instructed. My bad! 2nd charge with proper charger, not great result. 3rd charge seems to be working, used it twice for 15 min. each time over the past 5 hours and just checked and it's still doing the Energizer Bunny thing. If the charge holds I give this unit 5 stars. It is adjustably powerful and allows you to reach areas that would be inaccessible without an extra pair of hands. Main Negative... You can't use this without a C cable USB charger/adapter. They are difficult to find, even BestBuy did not have one. Jan 7/24 Ok... once I used the proper Adapter 5V/2A this unit has been flawless! This unit hits (hammers) the stubborn knots I get between my shoulder blade and spin. If you have to go it alone this is the unit for you!