Amazon.com: Structural Pipe Fitting, DIY Outdoor, Use Imagination -1-1/2"Tee-E Short, 3T-8, Aluminum Magnesium, Note: ID of fitting is 1.925, to take nominal 1-1/2" steel pipe which all have an OD of 1.9". :
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Aluminum Pipe Fittings Manufacturers and Suppliers in the USA
Production Process and Advantages of Aluminum Pipe Fittings - Pipe Fittings - Henan Lanphan Technology Co. Ltd.
USA Industrials - Pipe Fitting: 1 x 1 x 1″ Fitting, 316 Stainless Steel - 28830149 - MSC Industrial Supply
Aluminium Pipe Fittings - Mahodaya Steel
Tee, 1 in For Pipe Size, Structural Pipe Fitting - 54WK29|5E-6 - Grainger