Product review (5 stars): Good for knowing your humidity levels
I just bought a new Martin acoustic guitar and really want to make sure its properly humidified  in the case when not being played. The neck on my last acoustic guitar warped terribly because I didn't humidify it at all from the start rendering it worthless now, luckily I didn't pay much for it from the get-go. I decided now that I've invested in an entry level instrument its time for proper humidification so I bought humidifcation products (headstock humidifer and body humidifer)but the problem was I didn't know what the percentage was in the case so I started to worry. This guy seems pretty accurate, I'm comparing it with a room humidity monitor I bought and seems to only be a 2-3% difference of the room humidity monitor. Not sure which is more accurate but now I have an idea of where my case humidity levels are which is giving me a lot of peace of mind. I'd suggest this for anyone unsure of their instrument case humidity levels.