APFs are always manufactured in a flexible material.

The decision to start treatment with APFs depends upon the motivation of the patient who will play an active role.

APFs have  two U-shaped troughs, linked at the base in a relationship of correct occlusion. Appliances have different shapes dependent upon the pathologies they are designed to correct.

The 6 types of appliances are:

- SB for mandibular retrognathism (class II)
- SB for mandibular prognathism (class III)
- SB for palatal expansion
- SB conformer (class I)
- Square APF for palatal expansion
- Square APF conformer (class I)

SB for mandibular prognathism

or classe III