upper seal is friction fit to the wiper to achieve the air tight seal for example the upper seal could surround the wiper flange 12 such that the air tight connection is achieved against the exterior of the wiper preferably however and as shown in fig4 b the upper seal is inserted into the upper orifice of the wiper and a friction fit is achieved between the exterior of the upper seal and the interior of the wiper this arrangement may create a more sleek less bulky appearance the upper seal 13 may be provided with a flange 15 that rests against the flange of the wiper 10 when the upper seal is fully seated on the wiper however the contact between the upper seal flange and the wiper flange is not the primary seal the upper seal flange merely limits the depth to which the upper seal can be inserted into the wiper the primary air tight seal occurs inside the wiper down a distance the upper seal also has a weakened portion 16 that can be pierced or punctured relatively easily with a sharp object in fig4 b the weakened portion is located a distance down into the upper seal the weakened portion is relative to the rest of the upper seal which cannot be pierced or punctured as easily as the weakened portion while an air tight friction fit exists between the upper.