HornBike Speaker Horn with Arm Band (Black) Ecofriendly silicone bicycle amplifier (no external power source required). Shockproof&#44; scratchproof&#44; and washable silicone. Features an adjustable strap to fit all bicycles and can be set in almost any angle.Bugle Using micro pattern&#44; the surface can show threedimensional patterns and would not lose colors. 100% Biodegradable.