
I am a physiotherapist and I have used many different goniometers. The only thing that set them apart from others I've used is that the plastic was thin, like a credit card so was flexible. I really didn't like it at first, but now that I'm using it, the flexibility allows me to adapt better to the patient's joints and position. I suspect it wasn't part of the intended design, it was probably made out of thinner plastic because it was cheaper, but it works to my advantage.