This detector identifies gas leaks with high and low sensitivity modes ranging from 50 to 500 ppm. It features a 75 dB audible alarm and a visual LCD alert for gas concentrations as low as 50 ppm. The compact, pen-type design allows for easy portability in a pocket or toolbox. The price drops from $25.99 to $18.99. Shipping is free for prime members, or it adds $6.