great product, very useful if you work in a noisy enviroment
I use models 15, 20 and 35. All work excellently, canceling surrounding noise and very good sound quality. I find 15 and 35 comfortable for wearing long term for hours on end, but model 20 is in ear and after a while is not comfortable.
I don't notice any improvement in 20 and 35 over 15, just more convenient in that it is Bluetooth, otherwise the original #15 is just as good.
Verified purchase: YesCondition: Pre-owned