Rigid caster wheel. Compatible with Vention's t-slot systems.
Vention is a Canadian company offering an online 3D platform for designing, building and ordering industrial equipment. They offer a fast turnaround for heavy assemblies, parts and systems. https://www.vention.io/
2nd model is one I modded in Orchard, Shortened the legs, added a support bead at the joints and rounded the wheel's edges.
Here is the link to the Orchard tree.