K&K Hot Spot

I have to confess I am using it maybe in an unorthodox way: I installed inside my strat, so I don't expect a great sound from it.
Compared to other piezos it has a good output and less quacky. Still not usable in an electric guitar but it's not meant for that. It requires a preamp

Pros
less quacky than cheap piezos

Cons
don't touch the jack or you get a huge noise. Maybe better the internal version

I use the pickup under the bass neck to pick up the slap sound. Very easy to fit and sounds great.

Bought this as a fingerboard pickup for double bass. Does not sound too bad and good for the price.
The downsides are that it is not a very loud pickup and the lead is very short which can be a pain if you want to connect it to a preamp