This kit includes every polygraphite or Delrin bushing available from Weltmeister and Racers Edge. The Weltmeister bushings are cast polygraphite and the Racers Edge bushings are a more precise machined Delrin. For a given application the Racers Edge Bushings will be more expensive. The 944SPEC-Bushings-4 kit features Weltmeister bushings where available and then fills in with the Racers Edge Bushings. The rear caster block is the factory 968 version which is an upgrade to the units used on the 944 series as it has less and harder rubber. The 944SPEC-Bushings-4 kit will feature Weltmeister bushings where available and then fill in with the Porsche Caster Block bushings....hence the difference in cost between the two kits.