I don't know what it is but I've used a couple hundred sheets of 8x10. Rated at 50, I developed it in Pyrocat HD 2:2:160 for 7min=N-, 8.5min=N, 11min=N+. I've developed it for 6min if the neg was rather hot. Great results, I found two defective sheets out of that group... Considering I paid only $1 a sheet for the last 100 I'd rate it a great value and wish I could buy more.