SAFETY MATERIAL: magnetic coral rack made of acrylic material, and harmless to fish and coral species, does not release and generate any substances. Matching screws do not contain metal material, will not oxidize. Adopt strong magnetic , can achieve strong adsorption does not fall off. Wonderful and practical accessory designed for making coral healthily. Easy and convenient to install, reliable in use. Adopt strong magnetic , can achieve strong adsorption does not fall off. Acrylic material, beautiful and elegant, , designed for aquarium fish tank. Item Type: Coral Rack Function: It can make coral healthily 4 Hole Size: . 7 x 7.7x5.5cm(L x W x H ) Applicable Glass Thickness: Maximum 15mm / 0.6in Colour:Transparent Material:Acrylic Package Contents: 1 x Acrylic Coral Rack 1 set x installing Magnet Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.