The balance beam is an artistic gymnastics apparatus, as well as the event performed using the apparatus. Both the apparatus and the event are sometimes simply referred to as "beam". The English abbreviation for the event in gymnastics scoring is BB. The beam is a small, thin beam which is typically raised from the floor on a leg or stand at both ends. The balance beam is only performed by female gymnasts. Beams are usually made of leather like material. Balance beams used in international gymnastics competitions must conform to the guidelines and specifications set forth by the International Gymnastics Federation Apparatus Norms brochure. Several companies manufacture and sell beams, including AAI (USA), Jannsen and Fritsen (Europe) and Acromat (Australia). Most gymnastics schools purchase and use balance beams that meet the FIG's standards, but some may also use beams with carpeted surfaces for practice situations. While learning new skills, gymnasts often work on low beams that have the same dimensions and surface of regulation apparatus, but are set a very short distance from the ground. They may also work on practice beams, mini beams, road beams, or even lines on a mat. Originally, the beam surface was plain polished wood. In earlier years, some gymnasts competed on a beam made of basketball-like material. However, this type of beam was eventually banned due to its extreme slipperiness. Since the 1980s, beams have been covered in leather or suede. In addition, they are now also sprung to accommodate the stress of high-difficulty tumbling and dance skills.