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Check the annual review.

Revenue by client: 18% FMG, 19% BHPB & 36% Rio Tinto
FMG and BHPB have culled large numbers in the last month so the revenue from that 37% will drop.

Revenue By Market Sector: 43% Mine & 47% Rail.
I'm assuming that rail associated with a mining project is still regarded as "Rail" These percentages may not change but the size of the overall pie will not be the same in the next couple of years due to reduced CAPEX from their 3 biggest clients.