Laser Check Stock, Blue Red Blue Prismatic, 24# Defense Safety. The check is at the top and two voucher below. 14 security features built into the paper. These include Fluorescent Fibers, Chemical stain protection and Thermochromic ink (Heat Sensitive) on the check face - Heat will fade the RED key image. And, Coin Reactive Ink in the back ? Key will appear underneath Coin Image in the endorsement area when rubbed with a coin.