The Testo 557 digital manifold has a 4-way valve block, large backlit display and sight glass. Two NTC thermistor clamp probes provide superior accuracy of simultaneous, real-time superheat and sub-cooling readings. An external vacuum probe provides fast and more reliable evacuation of the system. The wireless Bluetooth / App allows you to view measurement data on your Smartphone or Tablet, enabling you to quickly and conveniently complete and document your job. Then, be able to finalize the documentation and send the reports and invoice via email, right from the job site. In addition to the 60 refrigerant profiles stored in the instrument, the App can also be used to download new refrigerants from the Internet directly into the digital manifold.