A wiper blade comprising a base portion to be attached to a wiper arm, a lip portion to sweep away a water droplet or dust etc. The secondary coil includes different patterns such as a helical shape, a linear shape, and a circular arc shape. The bottom wall extends upwardly and inwardly from a location adjacent the perimeter to form a convex dome with an upper surface above the perimeter in the range of about 3\u2033 to 10\u2033. In another alternate embodiment, a witness groove measurement gauge is provided.