Shoei X-SPR Pro Rear Stabalizer - BlackShoei X SPR Pro Rear Stabalizer Rear Stabalizer to replace the original part or to customize the helmet individually. The rear Stabalizer serves the aerodynamic stabilisation and ventilation of the helmet. The airflow creates a negative pressure in the area behind the spoiler, which forces used air to exhaust from the inside of the helmet through the vents hidden underneath.