This is an simple under shelf storage mount for CO2 bottles.
This design uses 8mm rods for stability. I used 8mm aluminum rods (hollow) that I cut to a length of 27cm.
Scale the model if you use material that is known to shrink (I used ABS and printed at ≥ 101%). If your printer prints fairly accurate you should be fine or just need a few turns with a drill bit. Rod mounts are designed with 8.1mm diameter which worked fine for me.
I would recommend against PLA.
Material: ABS (PLA not recommended)
Print the designs with the flat side on the print bed and the mount pointing upwards.
Give the 8mm (length: ~27cm) rods a slight chamfer and gently push/twist the rods till the are fully seated in the mounts.