Designed for a specific use case, but the pipes used to make this weight holder/plate tree are likely standard sizes so the the end caps and footings might work for other pipes.

The PLA end caps fit into the inside of the metal circular pipes. Inner diameter about 47mm

The TPU footings fit on the outside of the metal square pipes. Outer length about 50x50mm

The TPU footings are softer than the original (I lost one of the originals which prompted the project) and much better to stub a toe on :)

This is the plate tree for reference https://www.marcypro.com/content/Product_Manuals/Weight_Racks/TSA-42.pdf