Amazon.com: Hot Rolled Steel Square Tubing, ASTM A-36, 1" x 1", 0.065" Wall, 12" Length : Industrial & Scientific
Everbilt 3/4 in. x 36 in. Plain Steel Square Tube with 1/16 in. Thick 801277 - The Home Depot
National Hardware 4067BC 1 in. x 48 in. Square Metal Tube, Plain Steel (Red) 16 Gauge, 215715 at Tractor Supply Co.
Hillman® Steel Perforated Square Tube at Menards®
Best 4x4 Square Steel Tubing Supplier | Sino East
Amazon.com: Prescott Plastics 1 1/2” (38.1 mm) Square Plastic Plug Insert, Black End Cap for Metal Tubing, Fences, Glide Protection for Chairs and Furnitures (10 Pack) : Industrial & Scientific
Hillman 3/4-in x 6-ft Plain Hot Rolled Steel Weldable Square Tube in the Tubes department at Lowes.com