a method of continuously forming a packaging sleeve of heat - shrinkable thermoplastic with an integral tear strip , the sleeve comprising a flattened tube having a first wall and second wall connected along parallel first and second lines of connection ; lines of weakness formed in the first and second walls proximate to one of the lines of connection ; the lines of weakness and the line of connection defining tear strip zones therebetween ; a reinforcing - levering band in the tear strip zones formed by welding superimposed portions of the first and second walls ; the reinforcing levering band being disposed parallel to the lines of weakness and in combination with the zones and lines of weakness establishing a tear strip for opening the sleeve .