Looks like OEM only solid chrome steel. I live in a winter-hostile environment due to road salt. Time will tell how long they stay rust free. Had to replace OEM due to swelling - 6 years later socket wrench was no longer available.
Pros
FEATURES: We use triple chrome plating with base coats of copper, nickel and chrome to ensure exceptional strength, beauty and resistance to corrosion. Constructed of cold forged and heat treated steel for dependable strength and durability, the paint does not chip easily.