The OS 52 four stroke piston ring will fit the OS 48 four stroke. They both have the same piston.

Most people on here buy their rings for any engine from Frank Bowman in New Mexico for half the price

Frank C Bowman
1211 N Allen Ave
Farmington, NM 87401-3568
505-327-0696
[email protected]


Here's the part on Tower's site

http://www3.towerhobbies.com/cgi-bin...?&I=LXCT37&P=7

While you are at it, did you know that the carburetor from a OS 52 or the Magnum 52 will bolt right up to the 48? The newer carbs are twin needle instead of air bleed.