Had some ~19mm O/D metal tube floating around the garage; so decided to put it to use.

The holes on the end brackets are meant to be snug on a 19.00-19.20mm tube. I tapped these on with a rubber mallet. The centre holes bracket holes are 20mm so can be slot onto the tube easily.

My shelf is 1.30m long and when fully loaded with heavy spools there is a little sag (less than ~10mm) so if using the same cheap tube that I am I would recommend placing a centre support bracket roughly every 1m.

I printed mine in the PLA-CF sample I got with the X1C. Each side is 78.35g and you have the centre-minimal is 61.5g. They do not need to be printed in CF, but I would recommend 0.28mm layer heights, at least 4 tops and bottoms and 4 or 5 walls. Remember, a full spool is roughly 1.25kg so a 1m shelf (15 spools) will weigh around 19kg.

Screw to wall with appropriate fixings for the wall. (I used 5x50mm wood screws - as my office walls are 18mm ply)