The backing is made of aluminum foil + glass cloth, which has higher intensity than pure aluminum foil. It is specially designed for sealing insulation joints and seams against moisture and vapor on foil-glass cloth, suitable for both HVAC and industrial application. 

Backing: aluminum foil + glass cloth 
Backing thickness: 110 micron / 125 micron 
Total thickness (backing +adhesive): 165 micron / 180 micron 
Adhesive: hot melt adhesive / solvent acrylic adhesive 
Option: non flame retardant adhesive / flame retardant adhesive