Update, I've got rid of these, they just don't respond to the low frequencies.
At first glance this a great little tuner because it is very small and accurate, possibly the most compact one available. And the display rotates electronically so you never have to read it upside down, wherever you mount it.
But the ratchet clip holding it to the headstock is weak and will spring off, I've lost one that way.
In the end I decided I wanted the unobtrusive small size so I took off the clip and fixed the body of the tuner to the rear of my headstock with Sugru, just behind the nut. This worked brilliantly, a permanent tuner on the guitar with nothing visible to the audience, easy to operate and read. But after a while the body of the tuner just came apart, they are held together with a snap fit which became weakened..
So I've bought another and this time I'll wipe a bit of Sugru into the seams to bond them together. Great product let down by poor construction.