3M 891 Series 2.54 x 2.54mm IDC Ribbon Cable Sockets. 891 series 2.54 x 2.54mm IDC ribbon cable sockets with military polarization and centre bumps. These 891 series IDC ribbon cable socket connectors have a double-recessed cover which allows cable to be terminated from either side and are supplied preassembled. Strain reliefs ( ; 192-7530 192-7530 typically) are available separately