Cooling shroud set for use with emissions system (PAIR) equipped GY6 125cc and 150cc GY6 4-stroke engines. This is the shroud set that Universal Parts brand 150cc replacement engines come with from the factory.PAIR is an acronym for Pulsed Secondary Air Injection System which is found on your cylinder head. It is an emissions control system used to lower HC and CO emissions. It works by allowing air into the exhaust flow.