<span style="font-family: verdana,geneva;">What is this mystery attachment? </span><span style="font-family: verdana,geneva;">All I know is that it goes onto a TriStar EXL, MG, CS & A101 Series</span>
That looks to me to be an elbow to an attachment that came with the TriStar....the ridges near the bottom give it away. Unless it is some sort of angle adapter to use with the dusting brush or upholstery nozzle.
I didn't even know the floor brush elbow can be removed until when I changed the plastic bristles with horsehair bristles. Once I removed the metal sole, I saw two screws that hold the elbow retainer.
I think the shorter elbow is better than the longer elbow.