they have a very tight seal even at temp. more so than non microcast. that is why they make more power.

from what I understand there have been piston failures at a higher rate with the microcast sets vs. the non- microcast pistons. not sure why?? i would tend to think that tighter seal would wear on the rod first with all the resistance- even at temp.

i have two NS3's and love them both- actually one Nova NS3 and a Top TS3. Could not see the extra $75 for 0.05 horsepower??