what is the mm of a stock 250r piston

[250r/master3]

just like i said it i need to know the mm of a stock 250r piston

[Dave310R]

I may be wrong, but I think it is 66mm.

[Bean]

66.00mm x 72.00mm is what the stock bore and stroke is

stock piston OD= 65.960-970 mm
(if i am reading the repair manual correctly)