PIPE DECOR 1 in. Black Iron Square Floor Flange (4-Pack) PDB SQFL-1-4 - The Home Depot
Steel Tube Connectors by Marni bemark, - Corner Joint 3 way Tube Connector (Galvanized) 25mm Tube Connectors are made of 2mm mild steel and is used on 25mm (1 inch) square tubing.
Source Hot sale stainless steel square pipe fitting square tube connectors 25mm*25mm pipe joint on m.alibaba.com