Torx size on A/C belt tensioner?

[Lloyd Bonafide]

Two days ago I changed the belts on my friend's 03 X3. As with all Bimmers, the job was fun and easy.

I ran into a hiccup though in that I didn't seem to have the proper tool for the A/C belt tensioner. I reached down there and the hole felt like a large Torx, however, my T50 didn't fit (seemed to be too small).

I was able to get it off with a hex, but that clearly was the improper way to do it, and I was wondering what size Torx is needed for the job.

Sorry if the answer to this has already been posted on the forums. I ran a search, but nothing turned up.

BTW, this is my first post!

[MJBMW]

torx 60!