Design Philosophy - Ride it all. The Hummvee Plus Helmet is at home on trails, mean-city streets and everywhere in between. Incorporates the MIPS Brain Protection System which is designed to reduce rotational motion transferred to the brain from angled impacts to the head. MIPS - MIPS Brain Protection System which is designed to reduce rotational motion transferred to the brain from angled impacts to the head. Airflow - An MTB helmet that¿s been designed with airflow in mind, the large vents maintain a linear flow of air to maximise breathability and comfort. Helmet Crash Replacement Scheme - If you’re unfortunate enough to be involved in an accident that causes damage to your Endura helmet, our Helmet Crash Replacement Scheme will reduce the cost of replacing your helmet with the same model or nearest model. Helmet Sizing S/M M/L L/XL Helmet Circumference (cm) 51 - 56 55 - 59 58 - 63 Helmet Circumference (in) 20 - 22 21.5 - 23.5 23 - 25. Ride it all. The Hummvee Plus Helmet is at home on trails mean-city streets and everywhere in between. Incorporates the MIPS Brain Protection System which is designed to reduce rotational motion transferred to the brain from angled impacts to the head. MIPS®MIPS® Brain Protection System which is designed to reduce rotational motion transferred to the brain from angled impacts to the head.AirflowAn MTB helmet that’s been designed with airflow in mind the large vents maintain a linear flow of air to maximise breathability and comfort.Helmet Crash Replacement SchemeIf you’re unfortunate enough to be involved in an accident that causes damage to your Endura helmet our Helmet Crash Replacement Scheme will reduce the cost of replacing your helmet with the same model or nearest model.  Lightweight in-mould construction   MIPS® Brain Protection System reducing multi-directional impacts   Removable adjustable visor offering a wide range of movement   Large vents keep your head cool in all conditions   One-handed micro adjust fit system with multiple anchor points for wide range of adjustment   Fast wicking quick dry soft touch removable padding   Covered by Endura’s Crash Replacement Policy and Endura Product Guarantee   Certified to CPSC and CE EN1078:2012 + A1:2012 Standards  Construction Main Polystyrene 50% Polycarbonate 25% Polypropylene 15% Nylon 5% Polyester 5%.Ride it all. The Hummvee Plus Helmet is at home on trails mean-city streets and everywhere in between. Incorporates the MIPS Brain Protection System which is designed to reduce rotational motion transferred to the brain from angled impacts to the head. MIPS®MIPS® Brain Protection System which is designed to reduce rotational motion transferred to the brain from angled impacts to the head.AirflowAn MTB helmet that’s been designed with airflow in mind the large vents maintain a linear flow of air to maximise breathability and comfort.Helmet Crash Replacement SchemeIf you’re unfortunate enough to be involved in an accident that causes damage to your Endura helmet our Helmet Crash Replacement Scheme will reduce the cost of replacing your helmet with the same model or nearest model.  Lightweight in-mould construction   MIPS® Brain Protection System reducing multi-directional impacts   Removable adjustable visor offering a wide range of movement   Large vents keep your head cool in all conditions   One-handed micro adjust fit system with multiple anchor points for wide range of adjustment   Fast wicking quick dry soft touch removable padding   Covered by Endura’s Crash Replacement Policy and Endura Product Guarantee   Certified to CPSC and CE EN1078:2012 + A1:2012 Standards  Construction Main Polystyrene 50% Polycarbonate 25% Polypropylene 15% Nylon 5% Polyester 5%.