The Forza Sports Replacement Rubber Speed Bag Bladder is an extra durable replacement bladder that is also lightweight. The bladder is affordable enough to keep a few replacements on hand, so you don't have to slow down your workout. Get your replacement speed bag bladder now and own a quality, durable speed bag bladder that you will love. The rubber valve will allow you to stitch the replacement rubber boxing bladder into your speed bag. This is an upgrade to the plastic version. Extra-durable replacement bladder. Replaces easily, holds air well and can really take a beating. Super lightweight and an affordable price makes it easy for you to keep 2 or 3 around for emergencies. Sizes:Small (Fits Bag Sizes 4"x 7" and 5"x 8") Medium (Fits Bag Sizes 6"x 9" and 7"x 10") Large (Fits Bag Sizes 8"x 11" and 10"x 12").