iMac Intel 27" EMC 2309 and 2374 Teardown
Quote from BradMacPro:
The web site says 12.7 mm while the original drive says 12.5 mm. Small difference, but could be a problem closing the case or aligning the disc in the slot.
I think they were just a bit lazy with the measurements here.. look at the image of the superdrive and google the code. I'm pretty sure that it is actualy a 12.7, not .5 (i've NEVER seen a 12.5 drive.. anywhere), so it will be a perfect fit.
I recommend the UJ-235A over the 135 they mention in the article too, as it can burn blu-ray discs at 4x.