The tsg evolution bmx helmet eaturing our custom low snug fit the evolution helmet is one of the slimmest hardshell designs available it39s a tough hardshell construction that curves anatomically correct around your head for a great fit and wearing comfort the evolution is shaped on all four sides of the helmet and fits without slipping or jiggling it is the shape and fit role model for most of our helmets but it39s not just all about the great shape as safety is still of param