Back action clasp is a modification of:
Back-action clasp

It is a modification of the ring clasp.
Here the minor connector is connected to the end of the clasp arm and the occlusal rest is left unsupported.

Disadvantages:

Lack of support to the occlusal rest reduces its function.
It has both biological and mechanical unsound principles.
Ring clasp
Embrasure clasp
Onlay clasp
Hairpin clasp