As FPC supplier  tells you that the below are the different options of the flexible circuits.

Single sided flexible circuits

The design of single sided flex circuits deal with one conductive layer of copper, which can be bonded in-between the two insulation layers or built using just one insulating layer of polyimide and an uncovered side.

Double sided flex circuits

This has two conductive layers as well as a polyimide insulation layer present between them. Here, the outer sides of the conductive layer can either have covers or be exposed.

Rigid flex circuits

This is called the rigid flexible circuits that feature a design that is slightly different and costs more than other options of flexible printed circuits. These models make use of at least two conductive layers. However, the insulation material that sandwiches each of the conductive elements could be either a flexible or rigid insulation.

Multilayer Flex Circuits

The multilayer flexible circuits combine the double sided and multiple layers (single layers). These connect at least three conductive layers that are flexible with the insulating layers present between each. The most appropriate solution to overcome crosstalk, crossovers, as well as shielding and impedance requirements.

Sculptured flex circuits

This combines the double- or single-sided flex, without or with PTH.