Any good mechanic will tell you — use the very best components available. DENSO First Time Fit® oxygen sensors are specifically designed to meet the challenging demands of today's engines. Each of DENSO oxygen sensors is constructed of the highest quality materials available. High-quality stainless steel, porous polytetrafluoroethylene (PTFE), fluorine rubber, aluminum oxide, high-grade platinum and ceramics are used in each DENSO First Time Fit® oxygen sensor. The bottom line is: DENSO produces the finest oxygen sensors in the world. How can DENSO say this? Because, in so many cases, DENSO designed, tested, and manufactured the OE unit.