Direct Bond
Transducers are directly bonded to the tank bottom or sides.  Most common in smaller systems, up to 40 gallon.  For service, the entire tank must be sent in for repair.

Immersible Transducers
Transducers are bonded to the radiating surface, and enclosed inside a stainless steel box that is installed in the cleaning tank by bulkhead, standpipe, or stainless steel braided cable.  The immersible transducer can be removed, and sent in for service.  Immersible transducers are usually used in large systems.