I have a friend that wants to know if the blaster he is buyin has been bored out or not, so im askin where can i find the piston size of the piston, where is it located???

 

If you look on the top of the piston it will be marked.
std means standard size. (no boring)
010, 020, 030, ect tells that is has been bored and to what size.

 

Unless the piston is very clean, your not going to be able to see the numbers on top of it unless you take the head off and scrape the carbon off, and different manufactures have different numbers, so good luck, you may have to just take the word of the seller here.