Sigma couplings are a strong and heavy-duty system that provides maximum reliability with minimum need for maintenance. This is achieved by use of easy to install corrosion resistant gaskets and carefully dimensioned individual parts of the coupling. The material of construction is selected based on the type of products being handled and the atmospheric conditions of installation area. For GMP application SS coupling with SS nuts and bolts are used. PTFE bellows are used to compensate for different thermal movement between glass and associated equipment, absorb vibrations from associated equipment or foundation. PTFE 'O' rings are the most widely used gaskets. They are manufactured from pure, high quality PTFE and offer almost identical properties corrosion resistance to borosilicate glass. Sigma Scientific Glass Pvt Ltd is a leading ISO 9001:2000 certified company engaged in manufacturing of borosilicate glass 3.3 industrial process equipment, process plants and mini-pilot plants in India for chemical industry since one decade.