? No. 98 levels have ground and graduated main vial ? All levels have cross test vial, except 4 size. 12 size of both series has in addition a plumb vial, and 18 size a double plumb vial ? Plumb vials on No. 98?12 and 18 levels are ground ? Main vials are adjustable for positive setting and housed in brass tube with friction fit closing cover to prevent breakage ? Level bases are seasoned castings with black wrinkle finish, accurately machined and finished on bearing surface ? An involute longitudinal groove between bearing flats provides accurate seating on round work.