These thermocouples in the picture are from the O&S so-called ¡°standard range¡± whereas the ones in my dummy loads are of the style (Miniature) UHF Acorn (or flying saucer) without long flying leads at one end but spaced around an annular
ring in the centre of the thermocouple glass. This style generally has a better high frequency capability up to 1GHz; the frequency limit for the standard range is not specified in the O&S catalogue that I have.