The PX01 Sunamp Optimino Heat Pump Key, compact at 25mm x 25mm x 15mm, ensures seamless integration between your Thermino xPlus unit and Phnix Greentherm R290 series heat pump, facilitating efficient heating solutions. Features & Benefits: Sunamp Optimino Heat Pump Key – Phnix Measures 25mm x 25mm x 15mm Enables seamless integration between your Thermino xPlus unit and a Phnix Greentherm R290 series heat pump Facilitates efficient heating solutions Enhances overall system performance