If you have a Singer 66  series model , make sure it has a Spoke hand wheel (Not Solid).  Belt  measures 13 3/4" circumference.

FREE BOBBIN WINDER RING WITH PURCHASE OF BELT!!!

 New original , Softer, better quality Black V-Belt that is oil and heat resistant. .   This is the best belt you can buy for your machine. Here are a few  models belt will fit. Models: 15-30,15-86, 15-87, 15-96, 15-97, 66 Series (Spoke hand wheel only), 127, 128, 99, 185, 192, 206, 306, 319, 327, 237, 239 With solid hand wheels.