Johnson's 3700 I-beam level was designed to be durable and easy to use - so much so that it has been the standard in the industry for over 30 years. Its heavy-duty aluminum frame ensures accuracy and is durable enough to withstand even the roughest jobsite abuse and that frame is protected by shock-absorbing end caps if the level is accidentally dropped. The level also comes equipped with replaceable, durable acrylic vials that are impact resistant along with a top-read window allowing the user to stand over the work to view the vials.