Is ProMaster a good brand?
From what I've been told, its a brand that's kinda big in America, and the quality isn't too poor. Like, its no Hoya, but for its price its worth it. The binoculars in particular seem to be a whole level above.
Who made ProMaster lenses?
Promaster lenses are made by a variety of manufacturers Tamron, Sigma, Tokina are all in the mix the Pro lenses are not a generation behind the prices savings is generated by no manufacturer or vendor having to pay to advertise & sell the lenses (usually better than 20% of the lens cost) The benefit is saving to you.