My delrins require the inner shell only. Poly bushings require inner and outer. Delrin is superior to urethane and used in many high performance OE applications.
They make aftermarket pivot pins that don't have the step down for the inner shell to be pressed on for use with poly bushings. No inner shell needed with those, they already have the correct diameter without it. I use the greasable pivots that are also available with poly bushings, no inner shell needed and the pin is the proper diameter so everything fits as intended.