[Moppie]

The original and factory replacement bushings are slightly cambered to better follow the direction of travel of the trailing arm.
They have to be installed the right way round, and come with a Left and Right hand side in the kit.

If put them in the wrong way round, they will wear out in about 6-18 months (better halfs father did that once to her old Civic).

Since the mounting in the arm, and on the car is also slightly cambered to follow the shape of the bush, I would worry about an aftermarket replacement that wasn't built the same way.