This is a specialty, multi purpose insert designed around some more difficult to use tumblers. This is designed for the Ozark 24Oz(will also fit the 36 and 64oz version) and HOGG Cola style bottles(only tested on the 25oz but should fit others since they have the same cap size).
The insert screws into the threads on the Ozark for a very secure fit so you don't have to worry about it vibrating off.
The Hogg cola bottle is a pressure fit onto the end of the model and uses 3/8in weather stripping to help hold it in place. It has a tapered end so that the pressure fit is very snug.
There are also two holes on the model for M3 screws(not required). These screws will secure the insert to your metal rod. Use M3 x 10mm screws so that they do not protrude.
There is also an PVC model included but it ONLY supports the Ozark, on that model you'll want to use M3 x 14mm or m3 x 16mm screws.