Type M20 steel beam guide rail (SBGR) is a TL-3 MASH Longitudinal barrier guide rail system. Type M20 SBGR is a version of the Midwest Guardrail System (MGS) with 20 cm (8 in) plastic blocks. Type M20 SBGR is to be installed in front of a slope of 3:1, if a greater slope up to 2:1 is present an alternative 2,438 mm (8 ft) post can be used.