Instruct: Classify the given review as either positive or negative.
Query: economic and accurate

I used this setup to excavate and set up forms for a series of concrete pads that covered an area of 22x46 feet. What they are selling here is two pieces of clear tubing, caps for the tubing, and a valve on one end to keep the water from escaping. It works. However you do need to keep the level of water on the reference end at the same point. I find renting an auto leveling rotating laser to be much faster when the job requires making multiple measurements, as in establishing a level plane. But the technical simplicity and accuracy of utilizing water levels is unmatched. I think next time I'll try a water level utilizing a reservoir like the one talked about on this link: [..]