There are two primary types of welding strands, known as Class K and Class M.
A Class K welding lead has strands sized at 30 American Wire Gauge. The jacket on a Class K lead usually comes in darker colors like black or red. Class K leads are also the most common type of welding cable you will encounter.
On the other hand, Class M welding leads use 34 AWG strands, which allow for increased durability and flexibility. Remember, with gauges, a high number equals a small diameter, so Class M strands are significantly thinner than Class K strands. Class M leads generally have brighter-colored jackets and tend to cost more than Class K strands.