Naraku 878-17-28 CVT Drive Belt for Long Case 50cc 1E40QMB 2-Stroke engines. Fits the Following Models and More. Adly : Air Tec 50, Jet 50, Silver Fox 50 and Thunder Bike 50 Please note: the belt is stamped 890-17-28 because the manufacturer marks their products with the outer diameter measurement. This belt is compatible with original belt number 23100-117-000. Please see our Warranty & Returns Policy.