Since permanent magnets are assembled, after energized, plunger can keep holding, even power off, it's a power-save type solenoid.
De-energized holding force is in the range of 0.24-24kg, 12 basic types and 18 sizes for selection.
Pull force can be increased by the union outcome of inside magnet force and solenoid.
please consult http://www.zonhen.com for the detailed information.