The 24-inch COMPOSITE Manhole Cover and Frame Assembly from Trumbull Industries can pass a 50,000-pound proof load test per AASHTO M-306, H-25, yet weighs only one-third of a comparable cast iron frame and lid. Four stainless bolts compress the lid to the O-ring seal to prevent infiltration. Its O-ring seal design eliminates infiltration through the bolt holes. The underside of the lid allows the attachment of flow monitoring/leak detection devices. It is an ideal solution for manholes where hydrogen sulfide gas has caused deterioration to standard cast iron manholes. 800/677-1799; www.trumbull-mfg.com.