Rebar (short for reinforcing bar), is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar's surface features a continuous series of ribs or indentations to promote a better bond with the concrete and reduce the risk of slippage. Rebars can be can be produced both in coils or lengths of sizes: 6, 8, 10, 12, 16.