UEETEK 10pcs Soft Elastic Training Golf Balls Indoor Practice, Foam (Yellow) Color: mainly yellow. Material: durable soft resin PU rubber. Ball diameter: about 42.6mm. Soft, light-weight and flexible golf balls, ideal indoor practice sports training balls for the golf ball lovers. They are soft and safe and won't break anything indoor or hit people to be hurt. Suitable for indoor exercise and children practice as well.