Made from 50% merino wool and 50% acrylic with polyester lining, Windstopper is designed to give maximum comfort and flexibility during play. The high quality design with Opti-Therm technology gives an extra layer of thermal comfort. With a windproof lining, the garment blocks out wind from the body and gives better heat insulation on cooler days. The pullover also has a Callaway logo on the right sleeve.