MMG BRAND Belt Size: 729 – 17.7 – 30 Quality made for high mileage and reliability. Oil and heat resistant Save time and money, go for quality. Please make sure this is the right size for your system. Returns not accepted. Product Description MMG BRAND. This is the standard replacement belt for the GY6 50cc 139QMB 4-stroke long case engine. These are used on Baja, JMstar, Jonway, Lance, NST, Peace, Roketa, Sunl, Tank, TNG, Vento, Baccio, VIP and many others. Note: Scooters with a long case usually have a 12″ – 16″ rear wheel. Length: 729mm/28.70″ Width: 17.7mm/0.70″ Angle: 30 degrees