size in mm
as you well know, cylinder bores are matched to the pistons.
... just meaning to say it's a close match with a specific clearance tolerance.
So when a good shop hones your cylinders, they'll likely want to have the applicable pistons at hand so they can get the size and piston-cylinder clearace within the allowed tolerance.
those 81.965 pistons will be too small.
"If you want to fix it with a rock, you have to stick to stone-age technology" -Anton
"...solving the latest crisis that is preventing my Airhead from taking me to the bar." -Beater-