The 615 ML Multilevel Drive-Point Ports have adual barb stem to allow the connection of 3/8" OD(9.5 mm) or 1/4" OD (6 mm) tubing. The 615 MLuses the same couplings and extensions as thestandard 615 Piezometers, but with a Drive-PointTip to thread onto the first extension, or Port.Formation water enters the port, passes into thestem, and up into the monitoring tube attachedto the stem to its static level. The 615 ML is alsoa good option for high resolution profiling of soilgas, or groundwater.