These packages were selected because they are popular brands, easy to find and they have different designs of cap. The containers are made of Polyethylene Terephthalate (PET) while the caps are made of Polypropylene (PP) The caps are flexible enough on the bases to allow a degree of deformation that is necessary for the opening. To open this type of package it is necessary to squeeze the side tabs of the cap. so that the lugs on the cap are deformed away from the container. While squeezing the cap it is also necessary to turn it. this way the cap's lugs override those on the container. enabling the opening