As you can see from the photos these are beautiful covers that hide the ugly steel wheels and give the wheels a modern 'black' look . The photo shows mine on original 16 inch wheels. The metal ring in the cap snaps into the top or bottom notch to adjust the tension in the wheel. The instructions aren't clear on this - the bottom notch is more tension, the top less tension (mine is on the top notch). You also need to align the curve of the metal circle with a single "bar" that is slightly wider for the air nozzle. ' to relieve stress. If you have trouble putting it on, do not bend the metal and try again. It should be moderately difficult to snap into your wheel, but not nearly impossible (I spent 15 minutes trying to figure that out). A rubber mallet helps, and the wide flathead really is one for getting the last few tight staples into the wheel (which shouldn't be necessary if the metal is bent). Mine are very tight and didn't fall off the horribly groomed California soil. highways :)