I have some of these LiPo batteries left over from a large order. They are the correct replacement for the U2 instrument wireless system from XVive, both transmitter and receiver. They actually have slightly more capacity, so you'll get a longer run before recharging. Earlier U2 systems had soldered in batteries, later versions have plug-in ones. These are compatible with both, although you will need to either solder them in, or twist the bare wires together securely, and insulate them with tape or shrink tubing. If you have moderate repair skills, you should be able to do the job yourself, and there are plenty of DIY videos online for the task. These are not appropriate for other Xvive products, as far as I know. $10 each, $18 for a pair, or $25 for three.