This category covers plastic types of rigid nonmetallic conduit, including straight conduit, elbows and other bends in sizes 1/2 to 6 (metric designators 16 to 155) inclusive, intended for installation underground as raceway for wire and cable in accordance with Articles 352 and 353 of ANSI/NFPA 70, "National Electrical Code" (NEC). This conduit may be: (1) polyvinyl chloride (PVC) Type A, Type EB or Schedule 40, or (2) high density polyethylene (HDPE) Schedule 40, Schedule 80, EPEC A, EPEC B.

The conduit is intended for underground use under the following conditions, as indicated in the Listing Mark: (1) when laid with its entire length in concrete in any location (Type A), (2) when laid with its entire length in concrete in outdoor trenches (Type EB) and (3) direct burial with or without being encased in concrete (HDPE Schedule 40, Schedule 80, EPEC A, EPEC B or PVC Schedule 40). The conduit is intended for use in ambient temperatures of 50°C or less.

Unless marked otherwise, Type A and HDPE Schedule 40, Schedule 80, EPEC A, EPEC B conduit is intended for use with wire rated 75°C or less. Type EB and Type A conduit, where encased in concrete in trenches outside of buildings, may be used with wire rated 90°C or less. HDPE Schedule 40, Schedule 80, EPEC A, EPEC B or PVC Schedule 40 conduit, when directly buried or encased in concrete in trenches outside of buildings, may be used with wire rated 90°C or less.