Cab serialiser box built by OBBM / Rock-Wire  on these forums. Connect 2 cabs in series and you can use two 4-ohm cabs together to give an 8-ohm load (they would give 2 ohms  in parallel) Two 8-ohm cabs would give a 16-ohm load.  If it wasn't obvious, these are speakon connectors and 1/4" jack  post free