Well I haven't seen this one before. Was scratching my head, trying to figure out what the 1-through-6 numbers were for on the inside handle face of these pliers. Then I managed to find the patent and read up on it. Turns out they are for measuring. Spread the handles to numeral 4, and it measures exactly 4 inches from handle tip to handle tip. And so on and so forth, 1 through 6. Kinda clever.