What is it for? Surely it can't be for measuring wsm temp, that's what the big temperature dial is for, that's built in. If it's for meat temp, how do you guys use it ?
The gasket was designed to accommodate the temperature probes, both meat and BBQ. An alternate BBQ probe (besides the thermometer on the lid)can be attached to the grate where the meat is placed. Also, a food probe can be placed directly into the meat. Weber calls it the Silicone Temperature Grommet. Below is a link to an example of the temperature probes used.