Which of the following appliances is not used for slow maxillary expansion?
Jack screw
Coffin spring
Quad helix appliance
Hyrax appliance
Hyrax appliance 
This type of expander uses the Hyrax (hygienic rapid expansion) screw. It has heavy wires that are adapted, welded and soldered to the palatal aspects of the bands in the permanent molars. It is used for Rapid palatal expansion.
Examples of slow expansion: 

Jack screw
Coﬃn spring
Quad helix appliance

Textbook of ORTHODONTICS Sridhar Premkumar