There are two types of voltage reducers...one is for electronic devices, like gauges. You will need a "Runtz" for each 6 volt electric gauges on your car. For 12 volt negative ground only.
The second type of reducer is the ceramic block style which is used only to operate 6 volt DC motors and fans on 12 volt DC. Never, ever use the ceramic block version for gauges, radios or lighting. A power surge will destroy the electronics when first turned on.
Screw type terminals. 1.5 ohm resistance, 4 amp max load, 25 watts.