This is not a product as such, but rather the experimental ultrasonic antifouling system developed and documented in these articles:
It is not always available, because it is quite time-consuming to build and I don’t always have transducers. I sometimes manufacture small batches of them to support experiments. It is now listed here because a number of people have asked about purchasing one by e-mail and I shipped them to both Europe and North America.
So far, this system has proven to be superior to many high-priced commercial offerings, but several experiments are still in progress on test case vessels and I may still improve it whenever an opportunity arises.