The Killerspin 203-21 44 / 55 mm Table Tennis Balls includes 2 oversized 44-Millimeter and 2 extra large 55-Millimeter balls per pack. These balls are great for training and outdoor play. The product comes with a 30-day limited warranty. Table tennis is a sport that can be enjoyed by individuals of any age and physical ability. Playing table tennis is a great way to stimulate the brain and promote quick thinking while improving hand eye coordination. Killerspin was built to bring youth and innovation to one of the world"s most beautiful sports, and to serve the table tennis player. The Chicago-based firm produces premium-quality table tennis equipment, sports apparel and media.