Thank you. If you reverse the set up of one, you will be able to see the set screw hole that is normally on the bottom and not visible.
The diameter of the holder is 3.7".
Thank you. Unfortunately, the specification sheets do not provide us with those measurements.
Typically once an item goes out of stock, they are replenished within 2-3 weeks' time. If it is not back in stock by that time, you are welcome to reach out to our online team direct at 1-800-430-3376 as they can check their database for an ETA if it is available.