Features: The inner layer of the double-layer practice ball is made of synthetic rubber material, which very durable and practical. This kind of wheel like balls is very sensitive to accidental strikes and is designed to help you see the sidelines clearly. Copy the size, weight, and feel of a real golf ball. The putter wheel can improve the accuracy of putting on the green. It will enhances any errors in the pushs rod by swinging and bending the rod surface. If the balls is hit correctly, it will go straight into the hole. Suitable for professional and personal golf practice, practical and durable. These golf balls are suitable for beginners to train indoors or outdoors. When practicing in low light environment, bright color can help you see the balls clearly. Improve your putting skills with our Putting Practice Flat Golf Training Balls. Specifications: Inner Material: Synthetic Rubber Outer Material: Sarinaterial Diameter: Approx. 4.2cm/1.65inch Thickness: Approx. 3cm/1.18inch Package Includes: 2x Golf Practice Balls note: Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item.