RESISTANCE: Solid block vials for best durability and accuracy to 0.5mm/m. Virtually unbreakable; the vials are factory set and require no further adjustment.READABILITY: Magnified centre vial maximizes vial readabilitySHOCKPROOF END CAPS: Manufactured from an ABS plastic core with over-molded TPR rubber to provide best shock resistance360 VIAL: Rotating vial for specific angle measurementsDURABLE: Aluminium extruded box beam body for ultimate durability; the box beam design avoids twisting.