RPM-921-B -Blue Road Pavement Marker/REFLECTOR Bidirectional. Price: $4.00. RPM-921-B. Availability: In Stock. Item #: RPM-921-B -. Bidirectional Blue Reflective Pavement Marker RPM-921-B Or Road Reflector Are Usually Used to indicate location of Fire Hydrant, and are mounted on the pavement adjacent to a Fire Hydrant area.