D'AddarioPW-CT-15 Guitar Tuner - NS Micro Guitar Sound Hole Tuner - For Acoustic Guitars, Ukuleles - Non Marring Sound Hole Clip - Quick & Accurate Tuning

This is an astonishing, simple and discreet bit of kit. It works on all the strings of a 12 string guitar which are known for being difficult to tune. You can also use it for open tuning. For the price you cannot go wrong. There is a warning on the box that the clip that holds the tuner in place can react and leave a mark on certain finishes. I've got it fitted on my 12 string guitar tuned down a semi tone. It's very accurate to my ear. I can't comment battery life as I have only just recently fitted it. In general most reviews are very positive about this tuner and I think it's worth the money.

Nice and unobtrusive soundhole tuner. Nicely thought out design. Works well and reasonable price. Display easy to see. Second one I've bought. Not sure how long the battery would last but easy enough to replace.

I do like this tuner. It is small and sits comfortably on the guitar. It is inconspicuous to an audience but easily seen by the player. It is a little fiddly to reach to power on and off, although it has an auto off, but i soon got the hang of it. I switch it off when tuned to save the battery. I had to adjust the clip to get it to grip my guitar. I really like it. It lives permanently on the guitar so it is always there for tuning.

This tuner fits inside the sound hole of acoustic guitars. It is very unobtrusive and does not damage the finish. It means that you can check tuning very easily without fuss.

A neat little tuner that clips on OK (Guild D-50). It has survived it's first pub gig and worked as advertised - easy to see the display in low light too.I think the key to this device is to fit it where there is a single thickness of wood. On my guitar there was only one point where there wasn't soundhole reinforcement strips underneath and the pickguard was not too close to the soundhole - you need at least 7.5mm from the edge of the soundhole to the pickguard (if fitted) to fit this - I hope this helps.Update: Still working fine 11 months and 70 gigs later and on original battery. Has only once fallen off and ended up rattling around inside the guitar like a 2 ton plectrum. It's fitted to a sound board that is 3mm thick - any thicker I think puts too much strain on the clip which is probably why some people have had them break (minimal instructions with product don't give any guidance on this, though I note that their website now says 3.81mm thickness)Update 2: Three years of use and still going strong and battery life is good - the only other issue I have found is if you are playing outside on a sunny day as during Covid, the display is very difficult to see. Hope this helps.

My Gibson has a thicker scratch board so tuner doesn’t grip well and ends up usually falling inside. Apart from this it’s really good. Robert. PS. Inside clip too small

I bought this to replace an old tuner Intelli tuner which, to my mind, nobody has beaten yet for ease of use and accuracy. Now, this micro sound hole tuner works well enough as an "approximate" tuning device but it has one major drawback which is not made plain in the description: it will not clip to a sound hole with a scratch plate. Seriously, this is a major and dismal oversight. Most modern acoustic guitars have a scratch plate and those scratch plates double the thickness of the breast at the sound hole. Not only that but the scratch plate does not, in most cases, come up to the edge of the sound hole. The upshot of this is that you can't clip this thing where it's meant to go: directly beneath your line of sight as you look down at the strings. So, I've had to clip it beneath the strings where it can’t easily be reached to turn it on by groping a finger under the strings - not exactly a graceful move when you're trying to look cool in front of an audience.Simply put, it works, but it's of little use - and it's expensive.Update:-And its grip on the guitar is not strong so eventually, it'll eventually fall off and you'll lose it - which is what has happened to mine

Thought this would be perfect, just sit at the bottom of the sound hole etc. BUT it’s quite difficult to see, especially outside and the tuning icons are not at all obvious, just a tiny icon that tells you up or down. A bit disappointing really.