Sure they are; they're rated for 24V, double the 12 volts we use.I have this. Has been solid for 2 years, for fairly frequent and long winching jobs. A Swiss builder I know has these on at least 50 vehicles (before anyone goes "iTs nOt rAtEd fOr tHoSe vOLtAgEs"...)
'gets a little more complicated with current rating. Hella rates this switch at 100 amps continuously (100 amps long term without melting). But you don't run winches continuously; they're all intermittent duty devices. Hella rates the switch at 1000 amps for 10 seconds or less. Usually winches are used most of the time at far below their rated pull, so draw far less than their rated maximum current load. If you're recovering a 6000 lb. truck, say, you're rarely using that much force (unless you're pulling it up vertically or it's really stuck in the mud). So they'll probably work most of the time.