This review is for the Knipex 6-inch Cobra Pliers. The Knipex offset-jaw design is unique in that it is a balanced symmetrical design. The upper jaw actually is centered in a slot in the lower jaw handle. This insures that no matter how much force is applied, the jaw faces always stay parallel. This is NOT the case in most other offset-jaw pliers such as the popular Ch*****Lo*** design. The "6-inch" Knipex plies actually measure 150 mm (5.9 inches) long. The jaw width is 6.6 mm (0.260 in.). Jaw opening is adjustible in 11 steps between 0 to a maximum (parallel opening) of 30 mm (1.18 in.). The pliers are made of forged steel and the word "VANDIN" is molded into one of the handles. Presumably that means they are made of Chrome-Vanadium steel alloy (CR-V) which is born out by the extremely hard surface and wear-resistant jaws.
These small pliers only weigh 148 grams (5.2 oz.) so are easy to carry in a pocket. They have a leverage factor of 4.8 to the center-line of the jaws, so a clamping force on the handles of 50 lbs, will provide a clamping force on a nut of 240 lbs. They are very solid and do not bend or become springy even under very heavy force.
The construction of these pliers obviously makes use of a very advanced manufacturing technology. As noted, the upper jaw handle is surrounded by the lower jaw handle on BOTH sides. The slot in the lower jaw is 4 mm wide, BUT the upper jaw end is 6.6 mm wide and the handle end is 9mm wide. It's seemingly impossible to construct this assembly from finished parts. Clearly Knipex must somehow forge and finish the pieces AFTER they are assembled. This difficult and probably expensive process pays off by making these pliers much stronger than other designs and keeps the jaw surfaces aligned perfectly no matter how much clamping force is applied. It's a remarkable, clever and unique design.
I use these to tighten and loosen hard to reach knurled chrome-plated jam nuts which are too thin and too close together to grip with conventional pliers. These work perfectly,
These are not inexpensive, but like most high-quality tools are a lifetime investment. They are made so well they probably will actually last several lifetimes, so in the end are a true bargain. Although these are hard-working tools, they are so well designed and constructed they border on being functional Art.