It's a little hard to parse. The device itself is well made with excellent materials, so it deserves a 5 in this regard. However, the potential difficulty lies in the means by which it holds the seal on the valve. As shown in the picture, squeeze the silver lever to open the clamps, squeeze and hold the valve to create a seal, then release the clamp lever and allow the handle to hold the device in place position while the tire is inflated. One tire works fine, the other doesn't. The differenceโฆ