Quick Release Axle, 1/2″ wide x 5 1/4″ Effective Length, Stainless Steel with SILVER ALUMINUM Push Button.Sold as each. To make sure this will fit on your chair following these steps:1- Measure the width of your rear wheel hub from bearing to bearing and also the wheel receiver tube, where the existing axle slides through on the frame of the wheelchair. Add the two numbers together to get the correct axle size for your wheels. You can also watch our video to make sure you are measuring correctly.2- Measure your current axle from under the nut to the beginning of the ball bearing. see picture above