Circumference : 25.12 inches (approx). Size : standard size, fits almost all adults. NOTE : WE USE MOTOR / RED OIL ON ALL OF OUR HELMETS TO PROTECT IT FROM THE RUST. Quality is a parameter where we make no compromises.The products that we offer to our clients are high in quality. Beautifully designed and of high performance. And Small items is send through India post it take 10-12 days. In case of any discrepancy arising out of our product, kindly do discuss it before leaving any Negative/Neutral Feedback. Please also check our other items we are deal in bulk.