The Allegro Manhole Ventilation Passthru (MVP) (Patent Pending) is designed to maintain and redirect air flow with minimal restrictions into manholes, sewers and tanks. The Allegro MVP combines three components: a low profile air vent, 90-degree elbow and built-in mounting — all in one unit. Once placed into the manhole,the elbow fits underneath the lower cross bar on the guardrail. The MVP is stabilized by placing the manhole cover onto one of the flat channel corners. Allegro Industries,, (800) 622-3530. Circle 264