Underlay or underlayment generally refers to a thin layer of cushioning made of materials such as sponge rubber, foam, felt, or crumb rubber; this material is laid beneath carpeting to provide comfort underfoot, to reduce wear on the carpet, and to provide insulation against sound, moisture, and heat.

1/8" 3mm EPE foam pad with aluminum lining

 15 cents / sq. ft.  Each roll is 100 sq. ft.

1/8" 3mm EVA black rubber pad with blue aluminum lining

25 cents / sq. ft.  Each roll is 100 sq. ft. 

2mm white rubber pad with aluminum lining 

35 cents / sq. ft.  Each roll is 100 sq. ft.