This is a replacement thermal fuse, sometimes called a thermal cut-off, for an Isomac espresso machine. These are an upgrade from the original fuses, simply because they are at the correct temperature rating (157 degree Celsius). The Isomac machines come with a too high rated fuse (184 degree Celsius) and as a result, the heating element will blow in many cases.
The thermal fuse on many of the Isomac espresso machines are located above the heating element. When you're replacing the thermal cut-off please remember to replace the insulated sleeve as it needs to be reused.