This solenoid in particular is fairly small, with a 30mm long body and a ‘captive’ armature with a return spring. This means that when activated with up to 24VDC, the solenoid moves and then the voltage is removed it springs back to the original position, which is quite handy. Many lower cost solenoids are only push type or only pull type and may not have a captive armature (it’ll fall out!) or don’t have a return spring. This one even has nice mounting tabs, its a great all-purpose solenoid.