Make sure of the diameter. The disc type are installed with the "dome"/convex facing out. You hammer on it and it expands like a giant welch plug (carbs). The cup type is just pressed/tapped in. if the hole has a ridge/a stop inside, I believe that means you have to use the disc.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn