V2 and gen 9 pistons?

What is the difference between a gen 9 and a v2 piston? Is there a size difference?
I see there are single and double o ring versions.
Any particularly better than the other?

The cylinder is the same length just the head on a gen9 is slightly longer. The piston is the same length. You can use a gen8/9 or wells piston.
It’s only when you start using high speed gears you need to worry about how many teeth on the piston/plunger.

Thanks Maystro just trying to get my head around this all. :+1: