Understand that welding rods are made in sizes ranging from 1/16- to 5/16-inch in diameter. For example, a welding rod might be identified as having a 1/16 E6011 electrode, with the "E" at the beginning of the number standing for "arc welding electrode."
Look at the four- or five-digit number following the "E." If it is a four-digit number, the first two numbers tell the minimum tensile strength, measured in thousands of pounds per square inch, of the weld that this rod can produce when stress-relieved. If it is a five-digit number, the first three numbers indicate the minimum tensile strength. For example, an arc welding rod that reads "E60XX" has a tensile strength of 60,000 psi, and one reading "E110XX" is rated at 110,000 psi.
Note that the next to the last digit tells in what position you can use the electrode: "EXX1X" can be used in all positions, "EXX2X" is used in flat and horizontal positions, and "EXX3X" is for flat welding.
Realize that the final two digits show what welding current the electrode can use. For example, "DC+" indicates DC reverse, electrode positive. When the electrode is negative, the electrical current travels from the rod down to the metal, and when the electrode is positive, the electrical current travels from the metal to the rod.