This is the replacement thermocouple for the digital thermometer we sell. It would likely work with other thermometers that use a K-type probe as well. The end of the probe on our digital thermometer is worn through the protective coating - but it seems to still be working fine. So I am not sure you need to replace it just because the wire is bare. If you are getting strange readings (if say when you check the temperature of boiling water), then a replacement is likely in order.
NOTE: the wire is rated up to 480 degrees, plenty of room to watch coffee go from 1st to 2nd to ... too much.
It is possible to get the wire to fail or melt so be careful what it comes in contact with. Make sure just the end of the wire is touching the bean mass to get a proper reading and to ensure long life of the thermoprobe.