If you really want to take care of your instruments, in particular those who involve wood, like guitars, pianos, woodwinds etc. it really nice to have both a hygrometer and the temperature. Recommanded ranges are nicely showed so that you're always in control of your working / storing environment. A must have if you work in a basement, where air refreshing isn't always easy. I wouldn't say it's build like a tank, tbh it's really on the light side, both in terms of weight and materials. But why should it be ? It's not supposed to be moved around anyway.
Overall, a nice gauge to have in your homestudio !