could u plez tell me the compresion of this piston?

[exrider008]

im getting a new pison for my 400ex and i was looking at this but it dose not tell me what compresion it is or how many cc's it is a .040 86mm pistion and i was wondering if u could tell me the cc's and compresion.
http://www.rockymountainatv.com/productDetail.do


Thanks!

EDIT: i need this info by the end of tonight cuz im ordering it tonight.

[underpowered]

linky no worky:confused:

but 86mm is a 406cc

[exrider008]

ok thats what i thought but i wasnt sure
Thanks alot!