I've been an inspector on federally funded road and bridge projects for almost 15 years and can attest to this tool's durability and accuracy.  Don't cheap out and get the Sears version.  This tool uses a different technology and it's accuracy is amazing.  Also, the Sears version can not be calibrated.  I often check my MD Smart Levels against the contractors and always find that they are dead on.  These things take a beating and if the level itself gets damaged you can easily replace the aluminum box level with a identical replacement making the tool virtually new again.  The only comparable product is the Stabila, which costs twice as much.  Don't listen to the reviewer who suggests that the $69 model is the same.  The Sears model isn't accurate enough for ADA compliance verification.