These are self contained units with all the fuses and relay wired in. However, as I have all my relays in one place I replaced the supplied [stand alone] relay holder with one on the new relay bank. This to keep everything in the same place and secured properly. Quite straightforward to fit but had to be careful to wire up correctly. Ran the wires to the seats along the bottom ridge in each respective seat area (the bit where the floor joins the angled side panel), and connected up to the 12v live, 12v switched and gnd buses.
Operation is by individual switches mounted to each side of the dashboard so both the driver and passenger can operate their own without reaching forward to the centre or to the underside of the dashboard.