All EVP.MOde Spec TAPP primaries are calibrated with +2mm rollers. Bigger rollers make the low end "quicker RPM's" but shift out quicker and lower the full shift RPM. This has to do with the angle of the arms combined with the weight difference of the rollers. The roller assembly consists of a roller, axle and two washers.
+2mm Rollers: Outside Diameter 17.5 mm, with a weight of 15.3 grams each
IMPORTANT - As with the ramp angle roller size must be done in pairs across from each other, failure to do so will result in an imbalance of the clutch and possibly failure.