From what I understand, currently, the Model X and Model S seats are the same. They are made in-house by Tesla. This is what my SC is telling me. They call it "X" in to "S" seating. I believe these newer style seats have been used in MS since Jan 2017 and the MX since inception. They have the motorized headrest. They are supposedly not backwards compatible with earlier seats according to my SC, who supposedly talked to engineering about it. I had a 2016 MS75D and made the mistake of buying it with the Classic seats (Gen 1.5), which I came to hate and was a deciding factor in selling the car. The Next Gen seats were available in the MS around the 2015/2016 timeframe (possibly earlier) and were made by Ricaro. Next Gen were supposedly backward compatible with earlier Gen1 seats (for $6k), but that part number kit is no longer available according to my local parts department. Hope this helps.