PowerSwing Bat Weights by Markwort. Cast iron bat weights are color-coordinated according to their respective weight. Use for training and building arm strength. Use on bats with diameter 2 1/8" or larger. Used by players in practice and in games in the On-Deck Circle to get the bat to feel lighter, creating a quicker swing through the hitting zone. 7 Different Weight Sizes from 4 oz to 28 oz Available. Sold Individually, Not as a Set