One Size Fits Most – Beautiful, Bright LED Fiber Optics – Shipping Weight 9 ounces. This is an officially licensed NFL flashing fiber optic cap. NFL Flashing fiber optic caps are a unique and innovative way to display the top team logos! These beautifully designed replica caps have been fiber optically enhanced to provide individual flashing points of light within your favorite team logo. They are manufactured with the finest quality hats and feature adjustable velcro enclosures with your team name on the back of the hat. If you prefer to be anonymous, simply turn the lights off with the convenient on/off switch inside, and your cap is virtually indistinguishable from a regular hat. Our fiber optic team caps are powered by a replaceable, lightweight watch style battery (CR2025). Each battery will provide over thirty hours of day or nighttime fun.