Enhance Your Precision: This innovative billiard training ball is designed to correct your stroke action, providing a realistic cueing experienceEfficient Practice Tool: Crafted from rubber that won't scratch your cue, this Billiard Stroke Exerciser allows you to presets practice angles without needing adjustments each time. It simulates real playing conditions by allowing the cue to pass through its center hole smoothly if executed correctlyInstant Skill Boost: With consistent use, you'll notice significant improvements in stability and develop better follow through habits. This Billiard Training Ball is suitable for players aiming to elevate their game quickly and effectivelyComplete Set for Comprehensive Training: The package includes 15 balls with diameters of 58 mm and inner diameters ranging from 15.5mm-18mm, providing everything you need for thorough practice sessions at home or in the clubEasy to Use: This Pool Training Balls is an essential tool for both beginners learning the skills and experienced players wanting to refine their skills Specification: Material: Rubber Size Chart: Sphere Diameter: 5.8 cm/2.28 inchInner Diameter:1.55 cm-1.8 cm/0.61 inch-0.71 inch Package Includes: 15Billiard Stroke Training Balls Note: Please allow slightly errors 1-2cm/0.39inch-0.79inch differences due to manual measurement.