If you do go for the Rs125 caliper you will have to weld a lug on the bottom of the arm for the torque arm, done this on a 21, Dan at Gecko imports use to sell the conversion kit, but don't think he does any more, Tyga do an under caliper mount for the 21, but not sure if they do for the 18 models, might be worth an enquiry. But as Andy said might be easier to get another swing arm, I wouldn't have thought 18 arms were going to cost an arm and a leg. ps, RS250 nf5 calipers are the same as 125.
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