That's a family. You need a list of outside diameters for the type of pipe that you use. Based on that list, you can create a family that adjusts to that diameter. The sizes can be handled by creating types in the family, or by creating types in a type catalog, or by using a lookup table. The length of the bar that connects the bracket with the top needs to be by instance, so that the user can stretch that distance after placing the hanger. The center of the bracket needs to be at the reference level in the family, so that you can set the elevation of the hanger to match the elevation of the pipe. Here's a quick sketch of the main parameters:

Alfredo Medina _________________________________________________________________ ______
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