Pair of aluminum drums, were on my 86’ Monte SS for over 10 years and about 15,000 miles in that time, no issues when pulled, converted the rear to disc brakes last year, finally decided to part with them.
I don’t have a micrometer to measure, can just say they worked fine as is. I’ve read of those using them without issues past the measured limit, although that I’m not certain of. I had them cut before putting them on.