Harv
In case you still haven`t got a definative answer, found this in the Brembo Cat:
Lever Ratio................................. Recomended Fitment
20mm..........................................OE twin caliper. Popular for road
18mm..........................................Raci ng twin caliper
16mm..........................................125c c+ / Supermoto single caliper
"18 is recomended for use with Brembo racing calipers and 20 for all other makes of caliper" hope it helps