Squishy baseballs are commonly made from EVA (ethylene‑vinyl acetate), polyester shells filled with foam, various foam materials (including mini foam), and neoprene for models designed for water or pool play.
Common sizes include roughly 3‑inch diameter baseballs and mini sizes about 1.6 inches (≈4 cm) in diameter.
Training squishy balls provide feedback in a few common ways: they may deform noticeably on off‑center hits (for example, popping into an egg shape), use pop‑back materials that visibly show impact, or have limited‑flight behavior so off‑center hits feel and perform differently than solid center contact.
Mini foam training balls around 4 cm in diameter (about 1.6 inches) are commonly listed as compatible with mini pitching machines; these mini balls are often sold in 50‑count packs.
Features that improve visibility and tracking include two‑tone hemispheres, bright neon or high‑contrast colors, and bold patterns that make spin and flight easier to see.
Durability varies by construction. Some training balls use pop‑back polymers that return to shape and are advertised to withstand thousands of hits, while others are described as more durable than hard plastic alternatives and suitable for multiple seasons of practice.