Fanrelol: This type of springs are used in the production of steel sofas and its material is carbon steel coils, which are placed in the sub-foam of the sofa and are individually connected to each other by means of special threads.

Fenerzigzag: this type is used in the production of automobile engineering and sofas, and the floor and support of sofas are used for more flexibility. Phenerzigzag are connected to the sofa frame by special metal or plastic fasteners.