The VT01 Optimino Heat Pump Key, compact at 25mm x 25mm x 15mm, ensures seamless integration between your Thermino xPlus unit and Vaillant Arotherm+ R290 series heat pump, facilitating efficient heating solutions. Features & Benefits: Sunamp Optimino Heat Pump Key – Vaillant – Measures 25mm x 25mm x 15mm – Enables seamless integration between your Thermino xPlus unit and a Vaillant Arotherm+ R290 series heat pump – Facilitates efficient heating solutions – Enhances overall system performance