Phonograph record a "De luxe" price. Later, Decca Records introduced vinyl Deccalite 78s, while other record companies used vinyl formulations trademarked as Metrolite, Merco Plastic, and Sav-o-flex, but these were mainly used to produce "unbreakable" children's records and special thin vinyl DJ pressings for shipment to radio stations. In the 1890s, the recording formats of the earliest (toy) discs were mainly 12.5 cm (nominally 5 inches) in diameter; by the mid-1890s, the discs were usually 7 inches (nominally 17.5 cm) in diameter. By 1910, the 10-inch (25.4 cm) record was by far the most popular standard, holding about of music or other
Hydraulic diameter also used in calculation of heat transfer in internal-flow problems. For a fully filled duct or pipe whose cross-section is a regular polygon, the hydraulic diameter is equivalent to the diameter of a circle inscribed within the wetted perimeter. Hydraulic diameter The hydraulic diameter, , is a commonly used term when handling flow in non-circular tubes and channels. Using this term, one can calculate many things in the same way as for a round tube. It is defined as where More intuitively, the hydraulic diameter can be understood as a function of the hydraulic radius , which is defined as