2" x 4â Rectangle Plastic End Cap Tube Pipe Inserts Rectangular Tube Plugs Black matte clean finish Two plugs per package Key Specifications: Top Size: 2â x 4" (51mm x 102mm) Over Height: 5/8" Compatible Inside Square Tube Dimensions: (1.62 to 1.75) x (3.62 to 3.75 id) Compatible Thickness Range: 8-12 gauge (Fits tubing with wall thickness of .164-.109) Size Based on Outside Dimensions: These caps are designed based on the outside dimensions of rectangle tubes. The plug insert end is about 1/8-1/4" smaller to fit inside dimensions, while the top dimension of the plug matches the OD dimension of the tube.
eBay