I have the previous version of this one it's the same but without the screen on the back. By the looks of it most models are almost exactly the same but with different logos or brand names.
It's battery powered & comes with a charger. I was also skeptical but I am very glad I brought it. Imo if you're getting into anything physical professionally you gotta invest in your body. Around 90% of injury comes from overtension & lack of mobility, Michael Jordan invested like 1.5 million a year into his health, don't skimp on it and at some point you will thank yourself.