110 BCD crankset, 46 tooth chainring (Surly steel single ring), 12-26 9 speed cassette. It worked fine for a month with no bash guard, then got so that it would throw it to the outside when I would be banging thru descending cog sizes, like every time I crested a hill and wanted fast acceleration for the following descent.

That was with a SRAM X9 RD, which would be a mid cage, I think.