Product review (5 stars): Bought with heater element, changed all three for good measure.
My heater element was broken, so I decided to buy these parts as well since they attach to the heat tube and are all wired in series with the heating element. Resistance levels on the old ones were much lower than the new ones. Old thermostat and high temp shutoff were about 1.5 ohms vs 4-ish ohms for new ones, so seemed to be a good idea to replace them all at the same time. Beats having to go in again to change if it later failed. Less than $50 for the whole shebang. Several videos on YouTube on how to perform the maintenance and was not a difficult job if you have basic skills.