Most duster coats consist of oilskin, a cotton or synthetic fabric treated with certain oils and minerals to make it water resistant. Some other duster fabrics are leather or untreated canvas.
Oilskin makers primarily used boiled linseed oil to coat their fabrics, but modern manufacturers often use polyvinyl chloride. They might add pigments during the coating process to add color. Leather is a durable option for dusters, and plain canvas is usually less expensive than oilskin and leather.
Dusters feature extra flaps over the front closure and shoulder areas to add extra weather protection. They are usually full length, and have slits in the back for easy wear in a saddle and leg straps to prevent flapping.