The poles of this chuck run the length of the chuck from end to end. Pole spacing up to 24" long is generally 1/4" magnetic steel and 1/16" nonmagnetic stainless steel. Pole spacing of 1/4" magnetic steel and 1/8" nonmagnetic stainless steel is used for larger chucks.Top plates are furnace brazed, making the magnetic and nonmagnetic steel into one solid, water-tight unit.