Stabila spirit level 2 vial is a smooth ribbed box section spirit level the ribbed profile provides extra strength preventing the profile from bending this spirit level can be used to check the horizontally of overhead surfaces by turning it and its horizontal vial upside down you can then measure precisely from underneath1 vertical vial and 1 horizontal vial measurement accuracy in the normal position 0029 05 mmm for overhead measurements 0043 075 mmm stabila patent vials that are moulded in