Comments about Sherwood Sherwood Magnum EX Purge Single Window Mask:
I am a snorkeler only. Still, the mask stays put and leak free when diving down in a reef or open water. Only gripe is it gets uncomfortable on my upper lip and bridge of the nose when I wear it for too long(45+ min). It could have something to do with my big head, but it has a fantastic seal that rarely leaks, and the purge valve is great to get any water out that might get in. Quite fog free compared to other masks I've used. I would definitely recommend this mask.
Comments about Sherwood Sherwood Magnum EX Purge Single Window Mask:
Very little leakage with my facial hair. I bought this one and the ScubaPro frameless. The SP doesn't leak at all though.