Show the World you ride a Micro! Micro Brand Helmets are Safe, Smart and Stylish and now available in a variety of colors and patterns. The Micro Helmet comes in: Small: 18″ – 20 ½” (Great for toddlers!) Micro’s quality branded helmets have the following features: Rugged & Durable ABS Outer Shell Fully Adjustable Straps Quick-Release Buckle Aerodynamic Design With Air Flow Vents Complies with ASTM standards for Bicycle Helmets as required by the U.S. CPSC