Mizuno RB 566 Golf BallsMizuno RB 566 Golf Balls The RB566 is an even softer feeling version of its predecessor with a new micro dimple configuration to maintain hang time past the apex of flight. With a softer yet higher energy core, the RB566 offers a great balance of high trajectory, soft feel and all round performance. Suitable for low to mid swing speeds, the RB 566 Golf Ball is great for maintaining distance, higher launch and straighter flight. New High Energy, Soft