Centric premium rotors utilize an Electrocoating finish that provides long lasting corrosion protection. E-coating is a superior electro-statically applied finish designed to withstand 400 hours of salt water exposure without rusting. Phosphate finishes utilized by other manufacturers provide only minimal protection from the elements; these finishes are generally only effective for the shipping and storage portion of a rotor’s life. The addition of heat and moisture eliminates the effectiveness of phosphate finishes resulting in immediate corrosion once installed in the vehicle. Premium rotors feature 100% fully machined finishes including rotor hats; This extra process provides better rotor balance and creates a cleaner, more finished looking component 2014 - 2016 BMW M3, 2015 - 2016 BMW M4, 2016 - 2017 BMW M2