Product review (5 stars): A Better Replacement
Since these parts are very well known to break (this is my third set in 4 years), it was great news to see that KitchenAid re-engineered the part to include a metal component! However, the hubs/axles and the rollers are still plastic.  The good news is that the hubs and rollers are attached to the metal portion with a small bolt, so if the plastic becomes brittle and breaks in another year (!), the fix would be to just replace the rollers by removing the bolt.  PLEASE TAKE NOTE: If you complain loud enough to KitchenAid, they will send you a set of rack adjusters for free. They still refuse to acknowledge that their product has an inherently flawed design, however! Very simple to install. Don't buy the Torx driver - a Torx bit comes with the kit.