Legal name: William Fredrick Rieflin
Also performs as: Biff
William "Bill" Rieflin (born September 30, 1960) is an American musician.
Rieflin came to prominience in the 1990s for his work mainly as a drummer with many notable groups in the industrial rock, experimental metal and related genres, including Ministry, the Revolting Cocks, Lard, KMFDM, Pigface, Swans, Chris Connelly, and Nine Inch Nails. He worked regularly with R.E.M. following the retirement of Bill Berry in 1997. As of 2013, he plays drums and occasional keyboards for the latest lineup of King Crimson.