I saw a planter on Amazon with this design for $140 and decided to make my own and print it. 

I split it in two in my slicer with dowels and used epoxy to join the parts. 

I've provided a .step file as well, so you can modify the railing mounts to your needs - Right now it is sized for a 40mm x 40mm railing

I printed in PETG, with PLA supports that i snugged into the model for minimal supports. I also used a modifier to increase infill around the mounting brackets.


Sizing Info
Railing Mount : 40x40mm

Long: 18"
Depth: 6"

Width: 5.2"

Screws: M3 25mm with nuts