Which piston size to get?

[ratmac]

My 2018 ec 250 has 101 hours on the stock piston and i Will be doing a topend.

This bike has never been torn apart. Is there a way to know which piston letter to get?

 

[Wbdisco]

Should have a stamp on the cylinder of which size is in it. A,B, or C.

 

[wade_wade]

Inspect and measure the bore prior to purchasing a piston.