This is the Coghlan&';s Six Function Whistle Essential Gear for Camping Backpacking Features: This whistle features an LED light, compass, magnifier, thermometer, and signal mirror along with a convenient lanyard and clip. Batteries are included. Uses 3x SR1121 x 1.5V button cell batteries This whistle features an LED light, compass, magnifier, thermometer, and signal mirror along with a convenient lanyard and clip. Batteries are included. Uses 3x SR1121 x 1.5V button cell batteries