The 25 series has been updated over the years. Older Harris 25 models have a seat assemble that consist of several individual parts. The newer Harris 25 models use an encapsulated seat assemble (Cartridge). Also, some of the older Harris 25 models have a fine thread 1/2-27 inlet connection, not a 1/4 NPT which is standard on all newer models.
Please verify which Harris 25 series regulator you have before purchasing inlet connection or repair kit.