Lazer Nirvana Forest Green MTB Helmet Large/X-Large 57-61cm. Lazer Nirvana Forest Green MTB Helmet Large/X-Large 57-61cm. Patent-pending Rollsys fit system is easily adjustable and very comfortable ! Rigidity Brace System: Reinforcements for a superior helmet resistance against multiple impacts. Internal Ventilation channels for optimum airflow with Antimicrobial and temperature regulating padding system ! Super Light Weight Only 260g ! 21 Large Vents with Integrated Tech Visor !