Mastering the use of a speedball for the first time can be challenging, but it can greatly improve your boxing skills such as hand-eye coordination and rhythm, and also help to build upper arm and shoulder strength. For optimal performance, a speedball should be cylindrical and inflated to the correct pressure, and must be regularly checked for inflation. The Runnerupenterprises Retro Series 8" speedball PB-SB4 is designed for more experienced boxers who already have a basic skill in using a larger speedball or speed bag. Made from genuine cowhide leather, it measures 8 inches in length, and can help to enhance and sharpen your hand-eye coordination, speed, and technique. The internal rubber bladder is safe model, which is designed to minimize air loss. The hanging loop is also a crucial feature, as it should be durable, but not too thick or wide, to prevent unnecessary friction that will wear out the loop and slow down the speed of the ball in motion.