Primo Remote Wireless Grill Thermometer

What is the difference between this and a Primo temperature controller?

This one measures and reports; a controller acts on the fire to hold a target. A remote thermometer means you know immediately that the grill has climbed, but closing the vent is still your job. If you want that correction handled for you, you are looking for a controller rather than a thermometer.

Which Primo grills does it work with?

Nothing in this listing ties it to a grill size, and a thermometer is not a fitted part in the way a gasket or a hinge kit is, so it goes wherever you are cooking. Owners of more than one grill generally buy one thermometer and move it between them rather than one per grill.

Do I still need an instant read thermometer?

Most people find they want both. A remote thermometer is for following a cook over hours from another room. An instant read is for the quick check that decides whether something comes off now, which is a different question asked at a different moment. Neither one does the other's job particularly well.

Why not just use the dome thermometer on the grill?

Because it measures the wrong thing. A dome gauge reads the air temperature inside the grill at the point where it is mounted, which tells you how the cook is running but nothing about the food. Doneness on a big cut is decided by what is happening in the centre of the meat, and only a probe in the meat reports that.

Is it only useful for overnight cooks?

That is where it earns its keep, but not the only place. Any cook long enough that you would rather be indoors, or one where opening the dome to check costs you heat you would rather keep, is a reasonable use. Roasts, whole birds and anything you are holding at temperature all qualify.