I do have one freshly rebuilt (by AirParts of LockHaven) M20C fuel sensor. Part no. is 610420-01, as were both the others that I installed, they are identical and work fine on either side. For the kind of flying I do (I commute to work, about an hour away, three to four times a month), the accuracy of the CIES units wasn't needed. I fly by time (as a previous poster recommended), but for my friends who have the CIES senders with a JPI 900/930 or similar, the accuracy is absolutely amazing. My rebuilt senders are much better than the malfunctioning ones, and in my own calibration test, five gallons per side indicated about 6 gallons in the left and 7 on the right. Yep, it's amazing 1930s technology! You know what you have plus or minus 1 to 10 gallons! Works great for my mission, may not for yours! Fun stuff, I love old school. If you decide to go old school (like I did), message me if you want a freshly rebuilt not-so-accurate sender! Enjoy your Mooney...