For anyone who sweats a lot and have to RMA their Index. I assume you're getting grey screen and that is because the Index is no longer tracking. That happens when sweat gets in the headset and dries into a crystalized salt compound of some sorts. It smudges the tracking components. One option is to open up the front panel of the index and use cotton swabs with rubbing alcohol to clean off the smudge on the tracking components. (the things that looks like green squares) I wouldn't recommend this since you can just RMA the headset. Future proof your Index by stuffing paper towels around the lenses so sweat doesn't get leaked into the headset.