Hollaender 52E-7 Extruded Wall Flange (4 Hole) Aluminum Magnesium 1-1/4" IPS

I used this to mount 10" caster wheels to some galvanized pipe for a heavy duty dolly to carry a 400 pound bounce house across the yard. It works well for mounting any flat surface to pipe. A rectangular rubber pad is included, a nice touch if you have a wall or surface to protect.