Custom conical wire springs are actually custom compression wire springs since their function is the exact same; they are made to compress under a load and to return to their original length once the load has been removed. The difference in this type of spring is that the outer diameters of the coils have been modified to where the spring has a cone/tapered shape. Also, due to the fact that the outer diameter, paired with the wire diameter, makes a difference in force, those coils which have a smaller diameter will be stronger and those with larger outer diameters will be weaker. This is because a coil with a tighter spring index is less flexible. That being said, since the coil diameters vary, the spring has a non-linear spring rate.