18.5mm complete carburetor and choke assembly. This is a carb for standard or performance applications on scooters that use CVK type carbs including:
Chinese brand 50cc 4 stroke scooters with engine designation QMB139 or 139QMB etc, which means nearly every Chinese 50cc (49cc) 4 stroke scooter.
Brands may include Ciclone, Meiduo, Fada, Sunny, JM Star, Meteor, 50QT, YYQT50, Huawin, Motostar, Baotian, Boatian, Solana, Arrow, Fierce, Forza, "Factory Built", Wolfboy, Qingqi, Kinroad, Lifan etc also other generic brands registered as "Moped" etc.
This carb will fit the standard rubber manifold on your 50cc scooter.