I have found the clip to be absolutely fine after ~50 pub gigs. What I like about it is that it is slightly elastic so you can fit it on the guitar, do up the screw to secure it, and then the elasticity allows you to very slightly bend it to take it off the guitar. Then you can put it back on easily the next time you use it by slightly bending it and you do not have to use the screw again. The rubber feet allow it to slide on and off the guitar without damaging it. This works well for me and it is very easy to use. I fix it to the lower bout (not the upper bout as is commonly shown in the photos), so by rights gravity ought to make it fall off, but it does not. Even set on the lower bout (which gives a better mic position in my opinion) it is very stable and has never fallen off while I am playing. This tells me the clip grips the guitar firmly and works very well. I am very happy with it.
It isn't sturdy enough to grip a guitar body, clamps should be much more rigid than this. The tiny litte screw to adjust the length falls out all the time, and is difficult to find again.
The 'rubber' (which looks more like plastic) is smooth and curved, probably the opposite of a good design for something that relies on friction... minimal surface area. Also it fell off soon after I opened the box, so I had to glue it back on.
It is very probable that you will knock it off the clamp and the mic will break, I recommend generous application of duct tape.
If Thomann made a metal version that was reliable I would pay £20-30 for it, because the mic is still worth having.
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