Well, the resident village idiot comes hat in hand, and bows to your collective wisdom. It was indeed just as you called it- the old cap still attached. When I first looked, I was looking from the top and I had a dentist mirror and flashlight so was up close. This looked like something that the filter would fit into. If I'd got my sorry a*s on the ground I wouldn't have wasted all of your time. Now to get a new o-ring. Thanks for the guidance- Dean