Someone somewhere was looking to identify a piston and sleeve set.

The piston is not 2 piece, that is a machined relief to prevent piston crown from scoring sleeve at temp.

These are for 70s vintage O.S. Max R/C and or stunt.
They interchange between cases, the .30 will fit .35 and the opposite is true.(sleeve od is same)
Crank rod pin all interchange.
Heads do not, the head and Sleeve have to be the same.

Part numbers are 30R/C code 22203002 and 35. 23003002.

Bore on the .30 is .734 approx
bore on .35 is.805 approx
This in inches not the foreign stuff.