I bought a stone gasket kit for my 1990 base model hatchback. I don't know all the contents such as the small o rings. Is there anyone who knows the content. I suspect some are injector o ring, but not quite sure. p/n is 06110-pm5-325.
There are often "extra" gaskets and o rings so they can sell the whole gasket set for more than one application. If you dont see that gasket while you are going through the engine, save it as an extra!
You can go to a place like hondapartsnow.com and see about looking up the part via part number and trying to find an OEM exploded diagram.