Heavy steel construction. The only disappointed I had, was trying to get it open. Every time I need to get into it, I must pry it open with a standard screw driver. Door fits very tightly it seems. So much so, that when I tried getting into it for the first time, I thought I had the wrong key or something. Either I got a bad one of the line, or there all like this. If they are all tight fitted doors, you might be disappointed like me.