what is this?

[400ex men]

hey guys win you see a Piston Kit what is say (87mm) are what is say (89.25) thanks

[mackspeed]

its called the bore... or basically the size of the piston, the bigger the piston the more displacement you get.

[plkmonster2]

Yup, its the bore, or the diameter of the piston in millimeters. 87mm is 416, and 89.25mm is a 440.