Amazon.com: Structural Pipe Fitting, 1-1/2" Heavy Duty Square Base Flange, 34F-8, Aluminum Magnesium, Please note. ID of fitting is 1.925, to take nominal 1-1/2" steel pipe which all have an OD of
TRI-Square (3-IN-1 Pipefitter Square) – Canada Welding Supply Inc.
Order Modified Pipe Fitter Square for Pipe Flanges – R.E. Lee Co