PKI 10 A Au, CAT I 4mm Chassis Mount Test Socket. Hirschmann Test and Measurementt PKI 10 A Au, CAT I 4mm gold plated chassis mount test sockets with pole clamp-claw edge and a captive insulated head and insulated ring, 2mm cross hole and M4 termination thread. These PKI 10 A Au series 4mm test sockets are ideally suited for insulated, non-rotating installation in equipment chassis and switch panels with a wall thicknesses of up to 2mm.. Rated voltage 30 VAC/ 60 VDC Rated Current 35A CAT I Screw mounting M4 Termination Thread