They attach at the nozzle and inject soap directly into the spray stream. Many listings describe a quick-snap connection so the dispenser snaps on and off easily.
Product details list materials such as plastic and ABS (Acrylonitrile Butadiene Styrene).
Kits commonly bundle the soap dispenser with accessories such as a multi-purpose cleaning brush, a window squeegee with sprayer, and power scrubbers or wheel-cleaning brushes for rims and wheels.
Soap attachments inject soap directly into the spray stream, so you don't need to pre-mix soap in a bucket or pull soapy water through the machine.
Descriptions call the dispensers lightweight and durable. Warranty lengths shown in listings range from a 30 Day Limited Warranty up to a 1 Year Limited Warranty.