Batting donut

A Batting donut is a weighty torus (or ring shaped like a donut) that is slipped over the handle of the bat to increase its weight. Players use such devices to loosen their muscles prior to batting in a game; once they step up to the plate after having removed the donut, the bat feels lighter and easier to swing. Batting donuts can often be seen lying in the on-deck circle.

Elston Howard is credited with its creation.