Sportsman's Warehouse Fishing Thermometer - A must-have tool for any fly angler. This thermometer will easily attach to a vest or a pack with a carabineer clip. Use this handy tool to check water temperatures to know when the fish are feeding. Avoid the trial and error of knowing if the water is the perfect temperature. 4 3/4in long x 1/2in round The temperature range is 20 F to 120 F or -10 C to 50 C