The Extech EX050 ExStik 16-Feet Extension Cable with Probe Guard/Weight For Extech DO600 Meter is an extension cable for measuring in solutions that are hard to reach. The EX050 is a 16ft (5m) cable with probe guard/weight, it attaches to ExStik meter for taking remote measurements, it helps keep electrode submerged and protected in liquid samples, and is not compatible with PH100 and PH110 meters and PH105, PH115 flat surface pH electrodes.