Par Aide® Sure Putt™ 10710 Practice Green System. Putting to the smaller cup, 3" (8 cm) diameter compared to a regulation cup of 4-1/4" (11 cm) diameter dramatically helps focus the golfer’s aim and trains them to make a more accurate putting stroke. The Sure Putt™ Practice Green System is a complete system that is widely regarded as the finest putting aid for any level of golfer.