This is a filament rack adapter that steps down to a ½" dowel from a ¾" dowel. I used Unhinged's model: https://makerworld.com/en/models/863417#profileId-814120 to build the bottom racks. I first needed to scale down his brackets for use with ¾" dowels. After I assembled two shelves worth, I noticed my smaller reels won't fit on the shelf. So I designed an adapter that's meant to be the top rack.