Built for durability and accuracy, the extendable box beam level adapts to fit jobs where standard lengths can't. The telescopic extension customizes the level's reach, while integrated rulers on both the frame and extension clearly show the total extended length—ideal for measuring and taking inside dimensions. A manual lock-out secures the extension at any desired length for repeatability. The magnified center vial ensures best-in-class visibility, and all vials are triple secured using our patented mounting system for unmatched durability and reliability. For accuracy, both gauging edges are precision-milled on the same plane, maintaining uniform contact across the full extended length.