Ionomers are hard, durable plastics that are used in golf ball manufacturing. Ionomer blends are used to form casing layers in premium, tour-played golf balls (Titleist models include Pro V1®, Pro V1x®, Pro V1x Left Dash and AVX®). Blends of ionomers are also used to form golf ball covers for many other golf ball models, including Titleist Velocity™, Tour Soft and TruFeel™.