Extends time of the vr big time. Bust bang for the buck.So you can truly run a Quest for hours and hours with this attached, that is the good news and at the price point that is very cheap gaming. The bad news is that its not the best harness in the world to attach to the Oculus strap. It has a velcro piece that lets it sit at the back of the head but the velcro is not really wide enough to even cover the distance across the headstrap so its something you need to carefully place to avoid the battery falling off.If they redesigned the harness with a wider piece of velcro this would be a perfect and cheap setup to extend gaming time.Light weight and fits nicely on the VR. Doesn’t weigh it down And gives you more playing time.So I know how to plug it in.But which of the two U S B ports goes to the headset. & What's the black button for. Does it automatically turn on and off or do I have to do it manually