A footbag is a small, round bag usually filled with plastic pellets or sand, which is kicked into the air as part of a competitive game or as a display of dexterity. "Hacky Sack" is the name of a brand of footbag popular in the 1970s (currently owned by Wham-O), which has since become a generic trademark.[1]
The most common game of footbag consists of two or more players standing in a circle and trying to keep the sack off the ground for as long as possible.