Abstract: A conversion kit is provided for installation of rotary shaft seals in stuffing boxes that normally utilize packing secured in place by a packing follower bolted to the stuffing box. In a preferred embodiment, the kit accommodates stuffing boxes of different sizes by providing a shaft mating ring having a plurality of stepped surfaces on opposing radial faces, each adapted to fit a specific size of stuffing box, with the inner annular surfaces lapped flat, a stepped adaptor ring which can be realigned to accommodate each particular stepped surface of the mating ring with which it forms a seal and gaskets sized to fit each stepped surface of the mating ring. During installation the packing follower is aligned in a reverse direction from its normal alignment so that the leg adjacent the shaft faces outwardly away from the stuffing box. It holds the adaptor ring in place to compress a gasket between the adaptor ring and mating ring and a gasket between the mating ring and stuffing box.