There have been a few posts from people lamenting squirrels getting into their feeders snd eating all the seed. DH and I came up with this way to keep them and raccoons off our feeders when we lived up north in wild country. Not a single one has been able to get past them in the 20+ years we have been using them. The tubes are too wide for the animals to hug them and climb.

They are 8" HVAC metal ducts. The house-like feeder pipe has a floor flange tha's screwed into the top of the pipe. Then the duct has a cap on it that sits on the flange. The whole thing is secured with bolts through the feeder tray.

For the other two feeders we fastened the ducts onto bells and secured them onto the pipes with grounding clamps.