beverages to be transported secure and freshly. All Sigg bottles manufactured after August 2008 use the "EcoCare" liner, which Sigg states is 'made from BPA-free and phthalate-free ingredients'. The disadvantage of thin aluminum is that it does not offer much insulation, which means that condensation can build on the outside of the bottle when cold drinks are transported, and hot drinks will result in a bottle which cannot be comfortably touched. Sigg sells insulating sleeves that protect the bottle from dents, help insulate the beverages inside them and eliminate the condensation issue. The limited size of the opening also makes it difficult to fill or clean the bottle or to use it for purposes other than drinking, though Sigg now makes wide-mouth bottles, and adapters that allow the use of the standard-size caps. Aluminum bottles are also more prone to dents than stainless steel bottles. Another disadvantage is that the bottles are unsuitable for freezing its contents, as freezing liquids expand in volume and cause the bottle to crack. Therefore, it is advisable not to keep fluids in the container during extended periods below freezing temperatures. Stainless steel bottles In 2013 SIGG introduced a new material into its collection, stainless steel. With the Hot & Cold line made of stainless steel SIGG offers a solution for insulated bottles. These bottles have a double wall vacuum insulation which allows them to keep temperatures, cold or hot, during several hours. One advantage of these bottles is that they do not need an inner liner to protect the liquids and they are more resistant against dents and scratches than the aluminum bottles. Polypropylene bottles Since April 2014 SIGG started manufacturing bottles made of high-grade 100% recyclable polypropylene, a safe, durable and eco-friendly plastic. As part of the philosophy of the company means to keep the swissness of its products, the SIGG VIVA bottles are produced in Switzerland. SIGG ensures that these bottles are free of BPA and they are produced with the same ecological standards of the aluminum bottles. These sport orientated bottles have the advantage that they are transparent allowing to see the inside and they are very resistant against dent and scratches. Glass bottle In 2015 SIGG the Swiss company enlarged its portfolio of product materials with presented a new bottle made of glass. The bottle consists of two walls of heat-resistant borosilicate glass, a WMB (wide mouth bottle) opening to