The ORS Oil/Water Interface Meter has a 100'long tape that is marked in 1/100' increments. The probe is 1" in diameter and the tape winds up neatly into an aluminum housing. The tape is released by opening the trigger brake that holds the tape in place and using the handle to uncoil the tape o the desired level. A continuous alarm indicates the probe has entered product such as DNAPL or LNAPL. An intermittent signal identifies that the probe tip has entered water. Measurements of depth to fluid are accurate to within 1/100" and can detect oil slicks as thin as 1/200".