A 45 is a 7 inch disc that is made from vinyl, a more malleable and flexible material than shellac. It was introduced by Victor in 1949, one year after Columbia had introduced the 12 inch LP, which played back at 33 r.p.m’s and could hold as much as 25 minutes of music per side. At 45 r.p.m’s, these new discs could hold up to 5 minutes of music per side, much like their shellac predecessors, but in a smaller carrier. LPs and 45s, also known as singles, required new phonographs to play them, so their introduction did not immediately mean the end of 78s. But by the late 1950s, the popularity of rock and roll—aimed at the young who preferred the new technology to the old—helped usher in the dominance of vinyl and the end of shellac.