Did you try normal sockets on it? I recently read (in preparation of possibly needing to pull the front seats out of an 07 Tahoe) that normal sockets will work on them. For said Tahoe iirc it's 13mm and 15mm as the front two are a different size than the rear two.
That tool's purpose is negated if you have a hammer. Couple well placed love taps and they come right off. That's how I got mine off anyway after seeing it mentioned.