Outer Layer Navy Blue Microfiber.
Middle Layer Nonwoven washable filter.
Innermost Layer Cotton.
Please refer to picture above to understand the sizing dimensions.
(S size) a = 15.5cm b = 9.5cm c = 5.5cm
(M size) a = 16cm b= 10cm c = 6cm
(L size) a = 18cm b= 12cm c = 6.5cm