Medium Hello Kitty Motorcycle Bicycle Bike 3/4 Helmet Retro Face White Sanrio Depth:10 cm / 4" Inner measurements: 21 x 17 cm / 8"1/4 x 6"11/16 Circumference: 57~60 cm / 22"7/16~23"5/8. One size fits all Material: ABS Front shield is included