The C3 series where used as a working mans protocol droid, lightly armoured to deal with harsh working environments, such as laser mining, heavy foresting and heavy manufacturing/construction work.
Being an older model if compared to the 3PO series, it's design features include only a single centre blue eye, bulkier shoulders with options for being armoured. The voice is male programmed due to the type of workplaces it is used for.
Colour- White/Dulled Silver
Type- Protocol droid