Additional Details ------------------------------ Product description: Fishers XLT-30 takes leak detection to a new level. Ultra sensitive sound microphones, combined with a non-distortion amplification system and crystal clear audio headphones make the XLT-30 the leak detector destined to set new standards for the leak professional.|Option C - About the size of a computer mouse, this small handheld sensor is de-signed for areas that the Big Foot Sensor can not fit into. The Little Foot assembly is normally used for leak detection inside buildings. Mute is activated by pressing the button in front of the Little Foot Assembly.