The surface devices pictured have been recognized in the NEC since at least 1940, Sec. 3369. In 1951 the new phrase " - - in existing buildings where the cable is concealed and fished- - " was added, with no record of the proposer or the reason. My opinion is that this splicing device may be OK for manufactured homes and mobile homes, but there is no place for it in normal wiring. How UL listed this is a mystery to me. Creighton
