With the B films rented at a flat fee (rather than the box office percentage basis of A films), rates could be set virtually guaranteeing the profitability of every B movie. The parallel practice of blind bidding largely freed the majors from worrying about their Bs' quality—even when booking in less than seasonal blocks, exhibitors had to buy most pictures sight unseen. The five largest studios—Metro-Goldwyn-Mayer, Paramount Pictures, Fox Film Corporation (20th Century Fox as of 1935), Warner Bros., and RKO Radio Pictures (descendant of FBO)—also belonged to companies with sizable theater chains, further securing the bottom line. Poverty Row studios, from modest outfits like Mascot Pictures, Tiffany Pictures, and Sono Art-World Wide Pictures down to shoestring operations, made exclusively B movies, serials, and other shorts, and also distributed totally independent productions and imported films. In no position to directly block book, they mostly sold regional distribution exclusivity to "states rights" firms, which in turn peddled blocks of movies to exhibitors, typically six or more pictures featuring the same star (a relative status on Poverty Row). Two "major-minors"—Universal Studios and rising Columbia Pictures—had production lines roughly similar to, though somewhat better endowed than, the top Poverty Row studios. In contrast to the Big Five majors, Universal and Columbia had few or no theaters, though they did have top-rank film distribution exchanges. In the standard Golden Age model, the industry's top product, the A films, premiered at a small number of select first-run houses in major cities. Double features were not the rule at these prestigious venues. As described by Edward Jay Epstein, "During these first runs, films got their reviews, garnered publicity, and generated the word of mouth that served as the principal form of advertising." Then it was off to the subsequent-run market where the double feature prevailed. At the larger local venues controlled by the majors, movies might turn over on a weekly basis. At the thousands of smaller, independent theaters, programs often changed two or three times a week. To meet the constant demand for new B product, the low end of Poverty Row turned out a stream of micro-budget movies rarely much more than sixty minutes long; these were known as "quickies" for their tight production schedules—as short as four days. As Brian Taves describes, "Many of the poorest theaters, such as the 'grind houses' in the larger cities, screened a continuous program emphasizing action with no specific schedule, sometimes offering six quickies for a nickel in an all-night show that changed daily."