ASTM metric standards for billet-steel bars first appeared in ASTM A 615 in 1979. Metric bar sizes are based on multiples of 100 square millimeters. There are eight standard metric bars as compared with the 11 sizes in the current inch-pound standards. The first metric size falls between the current #3 and #4 bar sizes. The metric bars actually match the current inch-pound sizes quite closely except there are no metric size equivalents to the #7 and #10 bar sizes. Bar strengths are reported in megapascals (MPa). The current standard Grade 60 is equivalent to metric Grade 400. Potential exists for added costs during the transition period to metric construction because rebar producers will be required to carry dual inventories to meet customer demand. Other possible problems include contractors having trouble obtaining metric bars for smaller projects in some areas. Consider an engineered substitution of current inch-pound bar sizes in these cases to keep the construction on schedule.