The level bubble is based on an elementary principle of physics: a bubble inside a partially-filled container will always rise to the highest point of the surface. The position of the gas bubble in the fluid shows the angle and the direction in which the object is inclined with respect to the horizontal surface.
Bull's-eye levels are used to control the horizontal positioning of jigs, machines, devices, equipment and instruments. The range features different materials: anodised aluminium body, natural or black colour with smooth reference surface or with threaded pin (BEL-PM, BEL-BH, BEL-PH).
Another version holds the fluid in a polymethylmethacrylate (PMMA) fluid housing for use also on aerial platforms thanks to the low surface tension and density of the liquid contained within the bubble. is equipped with a large lenticular surface which gives it high visibility. The liquid contained within the bubble is characterised by low surface tension and density optimised for use also on aerial platforms. It comes with (BOL-MF) and without (BOL-PH) mounting flange.
Also in the family is a series with adjustment pin (BEL-AD) that allows the adjustment of the bubble acting as a pivot point. These are available in anodised aluminium, natural or black colour. Turning screws set into three rear threaded holes tilt the housing to level the device. Another version, BEL-MF, offers a mounting flange with anodised aluminium body, in natural or black colour, front or rear flange, and is said to be suitable for scales, tripods and precision instruments.
Among the series of screw-on levels are BEL-MS monodirectional levels with epoxy resin coating in black or grey, and the new BOL-MB monodirectional levels with polycarbonate (PC) body for fixed or adjustable mounting using steel springs and zinc-plated steel self-tapping screws. The transparent housing, in impact-resistant polycarbonate, allows to check the alignment of the bubble in front or side positions.