WULSTBAND - SEALING WITH LITTLE EDGE
This band, usually called Wulstband, is the contemporary version of the Flatband. On this band the edges have been tapered down to a very thin edge. This produces two advantages. The tapering removes the sharp outer edge that presses into the film while heating. It also acts to reduce the temperature of the band along its outer edges. Without tapering, the band edge will cause a thinning of the film along the edge of the seal thereby reducing the strength of the package. Failures that result are called "zipper failures".