These are installed in your cylinder head right above your intake ports. They help keep the heat from the cylinder head from cooking your fuel injectors. If you are having any machine work done to your cylinder head, these insulators have to be removed. Over the years they get brittle, the o-ring seals get crushed down and carbon builds up between them and the head. That combination makes them hard to remove without breaking them.
The o-rings are included with our full gasket set, otherwise order the o-rings with them. OE parts.