sE Electronics RF PRO Reflexion Filter Pro Portable Vocal BoothThe RF PRO BLK U is the industry standard portable acoustic treatment device for recording engineers, producers, and artists working in untreated rooms or needing additional isolation in professional studios. Since its 2006 invention, the Reflexion Filter has become the choice of top recording artists and engineers worldwide, relied upon for vocals, acoustic and electric guitars, amplifiers, drums, strings, brass, woodwinds, and room microphones.