The Lexan polycarbonate crystal card provides a surface to analyze/classify snow grains and also has a slope index, which allows you to determine slope angles from a topographical map. Snow crystals placed on the card become recognizable and sizable. Ideal for sunnier climates, the Lexan crystal card does not absorb as much radiation as the aluminum crystal card, which allows you to study snow crystals longer and more accurately. This small yet very informational tool will take your snow safety skills to a new level.