Cast-iron bearing housings serve as elements of the so called bearing units. These units are formed together with all kinds of insert ball bearings. Bearing housings can be divided into three types: P, F and T. P-type housings have fixing bores pointing out at right angle to the shaft axis, and they are commonly called “standing” bearing housings, whereas in the PA-version bores are made in the housing itself and in the A-type they are located in the housing’s flanges. The fixing bores of F-type bearing housings are arranged parallel to the shaft axis. Square-shaped F-type has four bores, FL-type shaped as an extended ellipse has two fixing bores and the circular FC-type bearing housing has four fixing bores. The most specific features has the T-type bearing housing, called a tension-fixing housing. T-shape and the ability of adjusting the tension through a special fixing are the most distinguishing features of this bearing housing. All housings are made of modified green cast iron and equipped with a valve delivering grease, whereas one shall pay special attention to the proper placement of the lubricating groove and bore in the mounted bearing. The designation structure of bearing units’ symbols the system of creating designations for ready-to-use bearing units bases on the rule of combining the symbols of individual parts of the bearing housing and bearing itself. CRAFT bearing housings can be filled with 2 types of insert bearing UC and UK.