Patented Glo-View vial surrounds illuminate in dim light making vials easy to readPowerful GripTight rare earth magnets hold to ferrous metal surfacesSuper strong 9" solid aluminum frame is Job Site ToughV-Groove frame fits on pipe and conduit3 vials read plumb, level and 45°Top-read window for easy viewingGlo-View allows for use in dark areasVials are illuminated by patented glow-in-the-dark surroundsNatural light or hand-held light sources re-charge the vial surrounds