Quoted from headdead:

I have been using the Harbor Freight ultrasonic 2.5 on almost every part in my EM and am pretty happy, but it would be handy to have a few different sized containers to squeeze into tight places. Has anybody tried this Sonic Soak device? You drop this transducer into your desired container of water. I suppose larger containers would require additional transducers, but for a single relay or score reel it could be handy. IF it works.
https://www.indiegogo.com/projects/sonic-soak-the-ultimate-ultrasonic-cleaning-tool#/
Note that the ad is very careful to avoid showing any actual results.
You can buy them on eBay for about 100,
Anybody try one or anything else like this?
I really like the idea but I am skeptical.

Quoted from j_m_:

from: https://www.upcorp.com/technical-information.html

it sounds like the transducers are directional, and since they cause bubbles to form, having them at the bottom of the tank (pointing upwards towards the parts suspended in a basket) gives the best results. I'm not sure if any of the transducers used radiate 360°