That thingamajig on a clarinet mouthpiece that's a real PITA
to adjust---you have to poke around on the bottom of the reed
and avoid touching the rails of the mouthpiece in order to align the reed correctly.
I have a Rovner ligature and I like the way it holds my reed. The only problem is, the ligature is made with some rubbery stuff and it sticks to the mouthpiece like your butt on a car seat on a hot summer day!