The purpose of this adapter /digital thermometer is to measure the water temperature in a brewing cycle approx 1-11/4 away from the coffee during an espresso brew cycle. Also, and EQUALLY IMPORTANT, it measures the temperature of the group head under idle conditions. It can easily and ONLY be installed in a fully exposed E61 brew group. The temperature variance at the espresso puck (cake) and the temperature sensor point is approximately 3-5 degrees Fahrenheit. Differently sized heat exchangers and gigeleurs corresponding to respective manufacturer's specifications may see a lesser or greater variance in temperature. Obviously, the temperature during an extraction process will vary over the length of the brew cycle.