"Button": This, like the "New Harmony", is a contraption conceived in a moment of genius. The wolf eliminator consists of two threaded half-buttons, one of which features a string slot. The two halves are simply screwed together over the string, and voila! Simple, painless, elegant.
Occasionally, it happens that the thread is not quite cleanly cut, which makes it impossible to tighten it all the way, causing a nasty rattle. This is definitely something to watch out for before you take your cello out of the shop.
Conclusion: This wolf eliminator, notwithstanding the fact that it is a one-size-fits-all, has worked well on most instruments I have tried it on. As with all the other models, there is some trial and error involved to determine the optimal string to use it on, as well as the best placement on the string. In my opinion, it is a close runner-up to the "New Harmony" in the "usability" category, and a winner visually!