ORIGINAL: twomanytoys
ok. I found some info about the ring. HPI also makes a motor that has an oil ring on an abc type piston. Its a nitro star 25. Picco and ofna also make some motors that are ringed. Its just an oil ring not a compression ring.
Please post links. I do believe you will find that they are just a grove in the piston like I stated above. I owned a HPI nitro star 25 and it only has the grove in the piston like I stated.