While industry materials have changed a basketball's composition over time, the design concepts underlying the ball's construction have remained constant since the Spalding Corporation first patented the design in 1929. Like their 20th-century predecessors, modern basketballs are composed from three layers of materials that vary slightly by manufacturer and model.
The composition of the outer layer, or ball cover, varies depending on the style of basketball and the intended playing surface. Quality basketballs that are destined for indoor play have a soft leather outer shell that offers superior grip. However, leather covers tend to wear very quickly on asphalt surfaces, so outdoor balls instead feature more durable rubber covers.
A layer of thread insulates the area between the outside ball cover and the inner bladder, adding a layer of protection that helps the ball retain its spherical shape. Nylon and polyester are typically used to create a symmetrical layer of winding over the bladder.
When you use a pump to inflate your basketball, the air travels inside the ball to inflate a spherical bladder housed under its surface. Bladders are typically made from butyl rubber, a synthetic type of rubber that retains air more efficiently than natural rubber.