Chronographs are used to measure the rate of fire and velocity of the BBs once it leaves the barrel of an airsoft gun to make sure you are within the limits when playing at airsoft arenas. All airsoft events have different rules and regulations on the velocity limits for each style of airsoft gun, so it's best to read beforehand and test each of your airsoft guns with a chronograph. It’s better to play it safe and know exactly how powerful your airsoft gun is before going all the way to the game and being denied entry. Chronographs are essential for players who like to upgrade or modify their airsoft guns, to ensure they are operating up to par after installation. Be confident in your rifles ability and pick yourself up a chronograph from Airsoft Station.