Features: A Loud Siren to draw people attention on street. Keep your kids from danger by warning or noticing others. Easy to fixed on the bicycles.Suitable for handlebars with a diameter of 22-24mm/0.87-0.94inch. Four button controling 4 tone of Polices whistles. When press button bike light emitted a 6 Redness and Blue LED Light with the effect of flickers and Polices whistles. This bike siren can quickly attract the attention of others through both sound and lighting, strengthens warning effect. Suitable for biking, city commuting, bikes; and it is very suitable for most people who usually ride Bicycles in night. Specifications: Materials: ABS, electronic component Length: 108mm/4.25inch Power supply: 2pcs AA batteries (not included) Suitable for handlebars with a diameter of 22-24mm/0.87-0.94inch Package Includes: 1pc Bike Light Electric Horn note: Please allow 1-2cm errors due to manual measurement, make surely that you not mind before order. Due to difference between different monitors, the picture may not reflect the actual color.