'BK' (i) was the designation of Allied convoys (together with a numerical and sometimes a literal suffix) plying the route from the White Sea to the Kola inlet, and as such reciprocals of the 'KB' (i) series (January 1943/January 1945).

An early example of the series was the BL.1S convoy of 9/11 January 1943 from Arkhangyel’sk to Murmansk with six transport vessels escorted by the British minesweepers Gleaner, Halcyon and Speedwell, and the Soviet destroyers Gromkiy and Kuybyshev, and Soviet minesweepers T-113 and T-114. A late example was the BK.41S5 convoy of 3/5 January 1945 from Arkhangyel’sk to Murmansk with 14 Allied merchant vessels escorted by the Soviet flotilla leader Baku, the destroyers Dostoiny, Boblenstny, Derszky, Deyatelny, Razumny, Razyaryonny, Uritsky and Zhivuchy, the Soviet minesweepers T-112 and T-113, and the Soviet submarine chasers BO-151 and BO-222.