Even wider than Series 17 tips, these tips have a steel blade welded onto the end. They can burn a groove up to 2.5mm (3/32") wide. They take a bit longer to heat up, but once heated they hold their heat better than a wire tip. They are also much stronger than a plain wire tip. The 6mm (15/64") tip holds heat a bit better than the 4mm (5/32"), but is not quite as nimble. Heavy duty cord recommended.