Let me be the first to say yes, I have tried it. I bought this on Ebay for $8 plus shipping. There were no instructions, so I did not pay any attention to the orientation of the rectangle that is mentioned above.
First let me say that it play nicely. My clarinet is a Selmer 9*. I played it A-B against my stock barrel, and it is pretty tough to say that it sounds different. But it does sound good. The intonation was spot on, even though the barrel I got was about 1.9 mm shorter that the stock barrel. This confused me, but I did enough playing against a tuner that I am certain that the shorter length had no effect on tuning in any of the octaves, or in altissimo. And I started on clarinet as a youngster, so I do not have the problem of playing flat when switching from sax to clarinet as alluded to in the Rovner ad. I rotated the barrel, and played the same phrase, and thought that maybe...maybe the horizontal position played a little more easily in altissimo, but if so, it was very slight.
For $8 I am very happy to have a 2nd barrel that plays well, and plays in tune. Would I have paid the $109 list price? Simply put, no, since a backup barrel seems like an unnecessary piece to own.