nate its a 15mm....I wacked at it for a good 30 minutes but no luck. I did do a good job of starting to round it off though, and gave up. These were put on way too tight, but once I get them off I will make sure to antiseize them. I'm gonna go ahead and get replacement bolts anyhow, but I will antiseize those.

99 Mystique LS T-Red ATX Duratec Mods: Hella stereo Mods K & N air filter w/intake pipe www.sounddomain.com/id/jongordo8