These are contact transducer pickups. There is no way you can clip one of� these onto the edge of a soundhole; because, it will be in your way of playing the guitar. However, since this pickup works by picking up frequencies due to the vibrations caused by the strings, you can clip it onto the headstock like you would a tuner. It actually works great and it sounds better than a lot of other types of pickups I've tried. However, no pickup, I don't care how expensive, can reproduce the true acoustic guitar sound. I found by clipping the pickup on the upper corner of the headstock (next to the "D" tuning key) reproduces an even volume among all six strings. Any other place on the headstock you will not hear the low notes from the E & A strings as strongly. And there is no feedback; I even played my guitar with the headstock only inches away from the amp. You can break the clip and attach the pickup to the lower bout with double sided adhesive tape. Had I known about these pickups long ago, I would have saved all that money I spent on all the other acoustic pickups I own. Absolutely a great buy at $1.99. I ordered 4, and I'm going to order 4 more.
I bought this for $1.50 on sale so it's great for what it is. Clipped on the upper part of my acoustic soundhole I got a very clear and full sounding tone. You'll definitely want to secure it with some tape or something but sounded great!
Thought I'd give this a try, bought 2. Works great! Amplified my resonator guitar by clipping to the headstock (nowhere good on the body to clip to), easy-peasy louder through an amp.
The other one got tried out on my friend's acoustic guitar, also clipped to the headstock, but also run through an equalizer guitar pedal (as a piezo pickup can sound rather "honky") and sounded almost GREAT (!)