The YSI Pro20i provides everything you need in a handheld dissolved oxygen meter. Ruggedness, simplicity and reliability are the cornerstones of the instrument's design. The Pro20i features an integral (i.e. built-in) cable whereas the Pro20 includes a detachable cable. The Pro20i instrument measures dissolved oxygen and temperature. The convenient One Touch Cal feature makes it extremely user-friendly and calibrates within 3 seconds. Choose from a variety of cable lengths, up to 10-meters. A graphic, backlit instrument display provides detailed messages and instructions. The instrument features a slip-proof rubber over-molded case with an IP-67 waterproof rating and undergoes a 1-meter drop test to ensure the instrument will withstand the harshest field conditions.