Stopper for Drying Rack Wheels

I initially needed wheels to raise the Drying Rack from the ground to prevent the cleaning robot from going over all the time.I found a perfect “DryWheels” design here https://makerworld.com/en/models/85049#profileId-90915I printed the DryWheels in TPU so then it was necessary a stopper to keep them in place. The file contains 4 stoppers 16mm internal diameter for traditional drying racks and 4 stoppers 7% smaller for smaller drying racks.I advise to add glue in between the pieces to set them securely