michael adams wrote on 14/11/2020 :
Which goes up to 120C Which suggests the pipes themselves can exceed
the temperature of boiling water which is 100C. Most other pipe
thermometers seem to go to 120C as well. Not that I'd claim to
understand how this makes any sense.

It doesn't make any sense, unless it is for use on steam pressurised
heating pipes. Maximum you get on a domestic heating system at the flow
from a boiler, is 80C.