with two grooves for compression ring and one oil control ring. the piston pin bore diameter and length are 40mm & 76mm. What's more, you can write anything you want in the piston chamber. If you want more information, please contact me. 
There are some details as follows:
Payment:T/T,L/C
Origin:Guangzhou, China
Samples:Free
Minimum Order: 100 PCS
Packing:Neutral packing