1 x Genuine Wanhao replacement thermocouple. These run from the Duplicator 4 motherboard up the loom and down onto the hotend where they are secured using an allen key. The thermocouple is one of the most sensitive parts of any 3D printer which can sometimes fail. This is a cure for the "Heater Error！My temperature reads are failing!..." message you sometimes get on your Duplicator 4 screen. We can supply a full guide to replacing your thermocouple on purchase and of course offer any support needed.