The LM 43U mount was the final design of mount used on U-boats .
The LM 43U mount is only known to be installed on U-boats ( U-821 , U-977 , U-1023 , U-1171 , U-1305 and U-1306 ) .
The LM 43U mount was the final design of mount used on U-boats and is only known to be installed on U-boats ( U-821 , U-977 , U-1023 , U-1171 , U-1305 and U-1306 ) .