Easy to use, rugged and reliable, the YSI Pro20i provides everything you need in a handheld instrument for the measurement of dissolved oxygen. User-friendly and convenient calibration routine and 50 data set memory. A true field instrument with IP67 waterproof, rubber over molded case, and 1-meter drop tests ensure durability to provide years of sampling even in the harshest field conditions. Features Include: Integral (i.e. built-in) cable with 1- 4- 10-m field cable; user-replaceable DO sensors One Touch Cal allows for easy DO calibrations within 3 seconds with the press of a button. Automatic barometric pressure compensation. Quick response times; 95% response time in approximately 8 seconds with standard membrane (fastest response time on the market) Stores 50 data sets; no need to write down data Large graphic, backlit display and glow in the dark keypad A true field instrument - the display is visible when wearing polarized sunglasses Tough. IP-67, impact-resistant, waterproof case. Waterproof with and without the battery cover Rubber over molded case provides extra durability Multiple languages: English, Spanish, French, and German 3-year instrument; 2-year integral cable; 1-year polarographic sensors; 6-month galvanic sensor warranty The Pro20i features an integral cable, but the Pro20 features a user-replaceable (i.e. detachable) cable. Longer cables are also available for the Pro20, as is a BOD probe/cable assembly.