This switch includes dome light or interior light circuit, headlights, running lights and dimmer for dash lights. There is a built in circuit breaker for headlights. Knob / Shaft combination, Synergy SeriesTM Bezel and Accent Rings, connector plug, contacts and complete diagram of all connections included. This switch is highly recommended over the old universal headlight switches that can't handle modern bulbs safely. Requires a .435" mounting hole.