The reason I flagged this product in the review is because it NOT really 8 1/4 inches. This hole saw is actually a metric size which is a little under 8 1/4", actually 8 3/16". This information is missing from Revain's product listing page. I bought this hole saw to make a hole for 8" boat view windows (requires an 8 1/4 hole). I'll get by with a hole saw and grinder, but I'd welcome more precision on the list.