Any difference between the two

Thanks all!

The difference is in the inner diameter of the holes that the barrel fits into.  Since the A2 barrel is significantly thicker than the A1 barrel at that point, the A2 sight base has larger holes.

Don't have the respective barrel diameters handy, and to be frank, I'm too tired at the moment to drag out the micrometer and respective barrels to measure, but I expect someone will have the measurements.

Suffice it to say, the two bases will not interchange.

Ok, that's enough for me... I shoulda been more specific,,, the height is the same??

Yes, the height is the same