I got mine from O'Reilly's auto parts, they were $6/ea. Same as Summit. I know some people have had problems like misfires or throwing OBD codes. I have had nothing but success with them, yesterday I drove half way across the state and got 22.36 MPG manually calculated. I couldn't believe it. Same today, I drove and had 21.88 MPG. No wind and 60-80 MPH. I would highly recommend. I believe E3-66 is the part no.