Jay, I'm not picturing exactly what you want, but I have found that
both a 13oz coffee can and an 18 oz cardboard "barrel" of oatmeal are
sized perfectly for a slip fit in 4" flex tubing (tight) and 4" rigid
hvac duct loose enough for a quick-connect. I have short lengths of
flex on each of two tools near the same gated 4" pipe, with the piece
of flex terminated with one of the cans. When I switch from my planer
to my bandsaw, I just slip the oatmeal can out of the rigid pipe, and
stick the coffee can in.

Good. This means I may be able to find bigger cans that will fit into
a 6" connection. I will go to BJ (a discounted shopping club) to see
if they sell big cans like that. Thanks for the idea.

Jay Chan