3M 8500 Series 2.54 x 2.54mm Polarized PCB Sockets. 8500 series 2.54 x 2.54mm polarized vertical PCB mount sockets with centre bump polarization and PCB retention feature. These 8500 series 2.54mm pitch PCB socket connectors mate with low profile shrouded headers and are used in boardstacking applications such as mother/daughter board. A keying plug is available, see stock number ; 828-0437 828-0437