I have enough Foundry and OG Ghurkas for two 10-man units that I got as a job-lot off EBay and they fit pretty well together. There is a slight difference in the size of pouches, weapons etc (but that is always true of 28mm figures from different companies). I'd happily use them in the same army, but in separate units as though physically they would mix, their weaponry etc would jar too together.