From what it says in the description, it reduces transmission by 100 times at 632.8nm which would be OD2. It will most likely be around the same for the rest of the red zone it covers. Of course, like you said it is from DX so I may very well be completely wrong. A general rule when buying glasses is to reduce the transmission to 5mW or less for whatever power you are using. For example, if you have a 300mW red and you want no more than 5mW to reach your eye if it happens to point there, you would need a factor of 60 reduction which is OD1.78. These therefore would be OK provided they are actually OD2 for reds up to 500mW. Anyone correct me if I'm wrong of course.