Very disappointed... I originally purchased a 4" birdhouse mount out of PVC. After a couple of weeks, I contacted them to see when it was shipping. They said it was back ordered and would take several more weeks. They offered a 4" wooden mount in replacement. Same form and fit.
Unfortunately a 4" wooden mount is only 3 1/2" internally. Doesn't fit a 4" PVC post. I contacted them and told them of the problem and they said I could send it back with a 20% restocking charge. This was their error for not publishing the internal dimension. Now I am stuck with shipping back the piece + restocking.
They have now corrected their literature.
If you can buy the same item anywhere else I would avoid Bluebird.