This ADD-ON Dual Color LED Light string set requires STARTER SET (sold separately) for operation. Up to seven ADD-ON strings can be used with one STARTER SET. Dual Color lights change from warm white to multicolor with the press of a button! These energy-efficient, long lasting LED bulbs feature 5 functions which operate by pressing a foot pedal: steady warm white; steady multicolor; fading warm white, fading warm white to multicolor; lights off. Indoor use only.