Thalassamania:It is standard ... metric. Also consider the EXO-26 which I think is the best of the bunch.
The EXO is really a Commercial/Navy diving mask. It is heavy and expensive.
Kirby Morgan also makes a mask called the M48 SuperMask. It is light weight compaired to the EXO, has less internal volume than the AGA (that means is it less bouyant) and it has a detachable regulator which allows you to go to a secondary air source under water or talk/breath on the surface. Oh, it also uses standard American fittings so you don't need any adapters like the metrec AGA.
You can install communications in the mask from a number of venders. I perfer to use an OTS hot mike because it provides the best clarity and will last a long time because it is a sealed unit.