Skull Fluorescent Valve Caps: The valve stem caps are made of glow-in-the-dark material, when your wheels start moving, they will automatically flash and create a circle of light to make your car/motorcycle/bike look beautiful. Wide Application: Fits most cars, buses, SUV, RVs, trucks, motorcycles bicycles and etc.. Help keeping the tires of vehicles at the proper inflating level. Glow In the dark Valve Stem Caps: Materials that glow in the dark, please let the valve stem caps absorb light under sunlight or electric lights for 2-3 minutes or more for the first time, and then place them in the dark for a brighter light. Easy to Install: Remove The original valve stem caps from the wheel and install the Skull Tire Valve Stem Caps without the need to borrow tools, the universal size can be screwed on by hand. Tip: If you have any questions, the customer service will answer you within 24 hours, please wait patiently