Inaccurate. Can't trust this product. So far I have never used a spirit level where the bubbles stick. The bubble separates. Slowly straighten the bubble. Will have to buy another brand. I do not recommend. Eventually I had 3 in a row on a line and they all read differently. 1 left 1 right 1 almost off center. A few clicks and one thing got right. Uses a normal level to check the line.