My Bontrager (not sure who makes it for them) freehub required an 11mm to remove. I could not find an 11mm, but a 7/16" (11.1125 mm) hex bit worked for me. When I bought the new freehub, it came with an 11mm hex bit.

The Bontrager freehub may be made by Hugi (so mumbled the wrench at the LBS).