Tripp Lite PLC19BK Plug-lock inserts prevent accidental disconnection of C20 plug-in power cords from C19 outlets BLACK color PLC19BK inserts ship in packages of 100 pieces Corrects loose-fitting IEC60320 power connections that could lead to accidental disconnection of power cables Plug-lock inserts strengthen the connection of your C20 plug-in device to any C19 outlet, keeping vital network equipment plugged in and running during routine rack access and maintenance Universal compatibility ensures proper fit and enhanced plug retention when used with any standard C20 plug and C19 outlet combination; no proprietary cables or outlets required