Amazon.com: OLYCRAFT 60pcs ABS Plastic Square Solid Bar Rods 1/2/3mm White ABS Plastic Square Tube Solid Square Tube Styrene Rod for DIY Sand Table Architectural Model Making : Tools & Home Improvement
1-3/4" On-Side Fiberglass Square Hollow Tube - Max-Gain Systems, Inc.
Prescott Plastics 2" Square Plastic Hole Plugs, Square Tubing Inserts, Black End Caps for Metal Tubing, Fences, Glide Protection from Chair Legs and Furniture (10 Pack) - Walmart.com
4pcs 45x45mm Square Tubing Tube Pipe End Plug Caps Inserts Black - Overstock - 18340145
10 Pack: (1" OD) 14-20 Gauge) Square Black Plastic Plug, (for Hole Size 0.85" - 0.92" ID) Tubing End Cap, Furniture Chair Glide Inserts | Fencing Post End Inserts | by SBD - SB Distribution Ltd.
Plastic square tube 50mm x 50mm x 3mm black
Amazon.com: 2"Inch (50mm) Square Plastic Hole Plugs Insert (20 Pack), Heavy Duty Black Hardware Plugs and Unistrut End Caps for Square Tubing, Glide Insert for Pipe Post, Chairs and Furniture by Prescott