The One K MIPS CCS Helmet features a matte Polycarbonate and Advanced ABS Composite outer shell; injection molded shell design; washable quick-dry, moisture wicking liner; stainless steel mesh; comfort padded harness with synthetic suede lining, hook & loop adjustment, and Fastex buckle; two front, one back, and two center stripe vents. One K Helmets boast the perfect synergy between advanced technology and aesthetically pleasing design. Certified to ASTM standards. Data and info provided by MIPS. Item Specifications: Sizing: Regular/Round - Is shaped for a head which has almost identical front-to-back and side-to-side measurements; Long/Oval - Is shaped for a head which is longer front-to-back (from forehead to the back of the skull) than it is side-to-side (ear to ear).