Denso First Time Fit Oxygen Sensors are designed to meet the increasing demands of today's engines. Each of our oxygen sensors is constructed of the highest quality materials available. High-quality stainless steel, porous polyetrafluoroethylene (PTFE), fluorine rubber, aluminum oxide, high-grade platinum and ceramics are used in each Denso oxygen sensor. The bottom line is that Denso produces the finest oxygen sensors in the world. We make this claim because, in many cases, we designed, tested, and manufactured the OE unit.