The Kierr Flex 300 door stopper is made of aluminum and has an elegant design. The Kierr Flex 200 and 300 series feature a hinged design, which makes it easier to open the door stopper when you want to walk through the door without having to remove it. Using the convenient twist knobs, you can securely tighten the door stops. You can mount the Flex 300 high on your door so that you, too, can easily walk through the door without having to open it. Additionally, you can fold it up for easy storage. The rubber protection on the flexible plastic clamps ensures a secure fit on plastic, wood, and aluminum surfaces—and even on window frames with rounded or beveled corners! Use in children’s rooms is at your own risk, partly due to parts that can come loose. This also applies to outward-opening windows, as the device could fall down.