These UK domestic adaptors allows you to connect your blue 16 amp power cables to domestic 13 amp plugs and sockets.
The inlet plug allows you to connect your 16 amp blue plug into a domestic 240v 13amp 3 pin socket, to provide power for pre-cooling your fridge etc. whilst still at home.
The outlet socket adaptor allows you to connect your 16 amp extension lead to a product that has a standard 13 amp domestic plug.