The aluminum 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. With the aluminum card version, you can expect durability and long term usage. This small yet very informational tool will take your snow safety skills to a new level.BCA designed it’s snow study tools in conjunction with North America’s most experienced avalanche educators. BCA snow study tools allow you to gather all of the data you need, without breaking the bank.