Play claim that these are the best rubber bouncing balls in the world! With a 90% bounce ratio, these balls are the perfect choice for all jugglers that want to practice bouncing. 
 
Also known as G-Force balls, they aren't affected by temperature and perform fantastically. They can be cleaned up really nicely with soap and water if they get dirty. 
The 60mm ball is a good choice for bouncers who like tricks with a lot of balls - the smaller diameter means there is less chance of collision and you can fit plenty in each hand.
Play Bouncing balls are a good quality prop for a low price.