USE 52MM PISTON KITS THAT ARE FOR XR50 OR CRF50 HONDA ENGINES, IF YOUR USING A 50CC HEAD USE A HONDA TYPE XR70 OR CRF70 52MM PISTON KITS IF YOUR USING A 70CC HEAD THE BOTTOM SKIRT ON THIS CYLINDER MEASURES 55MM SO IT IS THICKER THAN MOST 52MM CYLINDERS.. IT IS TOO THICK FOR STOCK HONDA CASES. WILL FIT ALL 50CC AND 70CC CHINA CLONES THE 49CM3 IS MOLDED IN/RAISED NOT PUNCHED INTO THE ALUMINUM THIS HAS THE HOLES FOR THE SKID PLATE OR GUARDS ON THE BOTTOM READY TO BOLT ON. WORKS WITH OUR BIG BORE CASES TOO # (BBCS) BIG_BORE CASE_SET (50CC/70CC/TRX90) 58MM_OPENING CDI_TYPE_CASES (BBCS) CLONE/52MM/CYL @ NEW IMPROVED OIL RETURN