This Rainbow Knit Hacky Sack is a ton of fun in a tiny package. Learning to use a hacky sack can also be great exercise. Fine tune your hacky sack skills and then wow your friends! Speaking of friends, this would be a great gift, too! This 2.5 inch round knit-woven hacky sack filled with plastic pebbles, makes a great activity for the beach, pool, event or just around the house. Great for your coordination and exercise.