FWIW, I bought an SRAM 36-tooth (Red Force/Rival/Apex, according to the listing; the package and chainring lack model names). It says it's 10-speed only, but I installed it on my 8 and it's worked well so far. The old one was a Shimano that claimed to be 9 or 10; it's 2.85 mm thick; the SRAM is 2.71. It's an inner, not a middle.