A rebar (short for reinforcing bar), is a common steel bar, and is regularly used as a tensioning device in concrete and masonry structures holding the concrete in compression. It’s available in Grade 40, Grade 60, and Grade 75 (which refers to the tensile strength), and comes most commonly in 3/8” diameter through 1-3/8”. The standard designation is ASTM A-615 for plain carbon. 

Welded wire mesh, or welded wire fabric, is a series of parallel longitudinal wires with accurate spacing welded to cross wires at the required spacing. Machines are used to produce the mesh with precise dimensional control. The product can result in considerable savings in time, labor and money. Standard building mesh comes in a 6” x 6” or a 4” x 4” spacing. The diameter of the wire for building mesh ranges from .134” to .225”. The standard designation is ASTM A82 for plain steel wire for concrete reinforcement.