This Color Correction Pack #1 contains 9 color correction gels. These gels are cut to 2" x 5" and can be used to change the color temperature of your flash to match various sources of light or to change the overall color of the light to create specific effects. CTO (Color Change Orange) gels are used to decrease the color temperature of your flash to match tungsten and incandescent lighting. CTB (Color Change Blue) gels are used to increase the color temperature of your flash to match overcast lighting outdoors. Plusgreen (Window Green) gels are used to match fluorescent lighting. Since fluorescent bulbs vary in the amount of green they emit, you will want to try the various strengths of Plusgreen gels to see what works best. This gel pack contains 1 each of the following Gels: Color Correction Gels Full CTO (converts 5500K to 2900K) 1/2 CTO (converts 5500K to 3800K) 1/4 CTO (converts 5500K to 4500K) Full CTB (converts 5500K to 7800K) 1/2 CTB (converts 5500K to 6400K) 1/4 CTB (converts 5500K to 5800K) Full Plusgreen (converts 5500K to roughly match fluorescent) 1/2 Plusgreen (converts 5500K to roughly match fluorescent) 1/4 Plusgreen (converts 5500K to roughly match fluorescent) Velcro Adhesive is not included with this item but is available in my other products.