The masseur that arrived yesterday was a good buy.
The machine works with two size AAA batteries. If you receive a 15-minute massage, the batteries last for three months according to the manual.
There are three massage modes, all of which are comfortable for my stiff shoulders. I feel fine after receiving the massages for one hour, so the batteries should be dead within on month.
On Sunday, I will buy some rechargeable batteries for the masseur.