Flukers Screen covers are made of durable metal to provide a secure habitat for your reptile or amphibian. its durable construction withstands high temperatures and heating devices while allowing excellent air circulation and reducing growth of mold and bacteria. Dimensions: 10 gallon (10 in L x 20 in W)20L/29 gallon (12 in L x 30 in W) 30 gallon (12 in L x 36 in W)40 gallon (18 in L x 36 in W)