Steel spring useful for the leveling of the printing surface or for the extruder pulley (allows to maintain the right compression on the incoming filament). Using them as supports for the printing table, they guarantee a printing surface at the right inclination or at the preferred inclination depending on the final use.
If used with m3 screws, it is better to use larger washers at the time of assembly, in order to have a firm grip without the possibility of spring release. A m4 screw is the maximum size recommended to still have a screw-spring clearance, which allows the spring to work properly during compression without jamming.