This model snaps firmly to a 18 mm in diameter cylinder object for supporting anything above it. In my case, I used it to support a shower shelf that was starting to slip downwards, and we were using bottles to keep it up beforehand. (Sorry for disgusting shower pic)

The top supporting part is 48mm in diameter.

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I printed it in a standing position with PLA, as it will only be a compression load from the top. Didn't use any supports or adhesion help. But a Brim could help a lot with adhesion.

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Designed in Onshape (Free Web CAD software)

I'll leave a link to the design document for easy edit;
https://cad.onshape.com/documents/4347dae44c79b23165171e1a/w/8c0b2f64199a3670cbc6c150/e/526696d6b958dbfa0226ac85

Onshape is free for private use, just setup an account and design away!

Feel free to do anything with the model :)