'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, destroyers Dostoinyi, Boblenstnyi, Derszki, Deyatelnyi, Razumnyi, Razyaryonnyi, Uritskyi and Zhivuchiy, Soviet minesweepers T-112 and T-113, and Soviet submarine chasers BO-151 and BO-222.