Scotchlite™ reflective material helmet trapezoids are retroreflective. That means millions of tiny microspheres with a mirror coating on one side reflect light back toward its source to create an intense reflection. That's why it's ideal for marking any hard, smooth surface. Choose red/orange, lime green or silver. Gall's reflective items meet NFPA compliance. Measures 1-7/8"H x 2-1/8"W. There are 12 per sheet. "Scotchlite" is a registered trademark of 3M®.