These brackets are for use with 1" dowels and 1/2" dowels. The brackets shown in the photos were printed by Shapeways in Strong & Flexible plastic. I once had brackets printed in regular PLA, but those became brittle and broke. I think PLA/PHA filament is a good substitute for Strong & Flexible.
I made three tables using these brackets 4 years ago. All of the tables have been in constant use since then. Two tables hold lamps and one has held my 22 1/2" TV for the last 3 years. Here is link to how I made my tables - link.