Nirve Skull and Crossbones Ornament Bike Light Skull & Crossbones handlebar or seatpost mount light ornament Red flashing LED bulbs in the eyeballs Mounts to most handlebars or seatposts or round tubes 1'' - 1 1/2'' (25.4-38.2mm) Batteries included This is a decorative ornament, not a safety light. Consult your local laws/ordinanaces for safety lighting requirements.