The BSM RM-Metal model is based on the British Range Master unit produced between 1965 and 1969, as used by Eric Clapton in John Mayall's Bluesbreakers. Eric also used the booster when playing in the legendary group Cream. Its biting, powerful sound is clearly in evidence on the Bluesbreakers "Beano" album. Blues rocker Rory Gallagher, Heavy Rock pioneer Tony Iommi and Brian May from Queen were also heavy users of the orginal Range Master unit. The long yearned for new edition, now issued under the name RM from BSM, includes the same OC44 germanium transistors as the the original 1965 version. The RM Metal is a modified '69er RM model like Mr. Iommi's unit, which he has used on his second Black Sabbath records and later. The RM Metal model is recommed for Nu-Rock, low dropped tunings and baritone guitars.