I have One CMI Tail, PART # 845236A1. It is factory Merc for the 500 EFI engine. It is new in the box and includes clamp, jumper hose and gasket. $200.

I assume from the Merc part number they are 500 Header tails?

That is what I determined when I did a part number search. I bought these thinking I was getting a set (Port and Starboard) but found out when they arrived that I had two starboard sides. I had originally said these were port side, but they are the short ones in a pair, which is the starboard side. You can verify the part number and description on BAM.