Bob points out the "iffyness" of the enhanced coatings. Many of the "primo" mirror makers today will not put the enhanced coatings on their mirrors because they "can" introduce wavefront errors that essentially wipe out their work and reputation. That said, my first mirror 30 years ago had a 98% coating from a company no longer in business. It turned out excellent, and as a matter of fact, the guy who has that old scope says it is still going strong and has never been re-coated. But, I've heard similiar testimonials about the Beral coatings. Think about it, how long has Clausing been in business. He must know what he's doing!!