The Driveline Plyo Care Balls Set of 5 is designed for baseball arm strength training, specifically for pitching. Made of rubber and weighing 100-2000 grams each, these multicolor balls are suitable for both indoor and outdoor use. The set includes 5 Plyo-Balls, and each ball is designed with a weighted feature for advanced training. This set is ideal for players looking to improve their pitching skills. The Driveline brand ensures quality and durability in this sport-specific training aid.