It's a K&K mandolin pickup. The transducers for this pickup are quite different from the ones for their steel string guitar pickups. Quite a bit bigger surface area and a different shape.

I don't know yet. This is the first time for me using their mando pickup. Even when this instrument is up and running, it might not fully answer your question. The instrument I'm building is an octave mandolin with a flat top guitar type body with a fixed bridge. The K&K pickup seems to be intended primarily for carved top regular mandolins and the transducers are supposed to be mounted to the underside of the top just inboard of each f-hole. I talked to a guy at K&K tech support and told him what I'm building. I asked if I should mount the transducers on the bridge plate directly under the saddle like you do with the guitar transducers and he said no. He recommended placing them on the bridge plate as far out to the ends of the bridge wings as the bracing allows.

An interesting difference in installation between the mandolin and guitar pickups is that while they recommend installing the guitar transducers with super glue gel for best performance and maximum output, the mandolin transducers are installed with two layers of very thin double stick tape (provided) and the tape is required for best performance. They say that the tape cuts down on noise caused by things like brushing against the top. To make the installation more permanent, you have the option of adding a drop of super glue onto the tape, but the tape is still required.

As an aside, I asked about using their ukulele pickup mounting it under the saddle like the guitar pickup, but he said the frequency response would be wrong for a mandolin.

Interesting. They told me they placed them there because that's as far as you can reach through the f-holes, and to put a transducer between each pair like the guitars...which I did and it was fine.

Hey billm, that's looking like a great pair.
I'm guessing Bubinga and Sapelle with EIR bindings?
Looks like the side purfling mitres turned out well.

Just finished #84, a Sitka/double side (Mahogany outer IRW inner) size 2. Little guy. Sounds good to my moderately impaired hearing

I have been messing around with different wood combinations for double sides. Bird's Eye Maple outer/IRW inner has been a big hit. I like the Mahogany/IRW too but not totally convinced it is all that much better than straight Mahogany for both. Onward and upward eh?