Civic EG

so im planning to buy a high compression kit for my B16a engine,

my question is: whats a safe piston choice 81, 81.5 or 82mm? without doing any work on the actual block itself

im looking at this kit : http://fjdistributors.com/product_info. ... cts_id=212
is it any good? what compression should i expect?
sorry if i sound noob

The size of the piston depends on the bore of your block. For example if your block has high mileage, you may want the machine shop to bore .020 over for fresh cylinder walls. (over time they can wear slightly out of round)
Boring .020 will add .5mm to the cyl bore and you will need .5mm larger piston. You'll also gain a very small amount of displacement.

To add to Teal's remark, if you can get away with it, and the cylinders aren't too far out of round, have the machine shop take as little off the cylinder walls as possible to keep the rebuilding option still there in the future.