Outside layer stainless steel tube Inside layer galvanized steel tube. Especially design for shower room, bathtub,wash basin, etc Not suitable for slope ceiling. Especially for organizing Super Tall / Large / Deep bottles of shampoo, lotions, oil, body wash, towels, wash cloths, ETC.FEATURE: DIY ASSEMBLING,NO NEED ANY INSTALL TOOLS: no punching, easy installation, no tools required for installation. Do not hurt the ceiling. Make full use of corners and take up no space.