SKLZ Weighted Training Balls help build arm strength while playing long toss or during shorter throwing drills. Constructed with the same raised seams and leather cover as a regulation baseballs to provide the feel of a real baseball during training. Easily incorporate the Weighted Baseballs into training or pre-game warm up. 2-pack includes a 10 oz and a 12 oz version, compared to the regulation 5 oz weight.