Chrome 12 Volt LED License Plate Fasteners. Have you been thinking about the need for a license plate fastener that is a little bit different than everybody else? Well, here you go! These are 12 volt LEDs. Maybe you would rather use them for under hood accent lighting? Trunk? Interior? They measure about 1 3/16" long x 1" outside diameter. The shaft size is 1/4". The listing is for two.