A storm stay is a device that is used to hold a window or door closed in strong winds or during a storm. It is typically used on windows or doors that are located in areas that are prone to strong winds or severe weather. The stay is typically installed on the side of the window or door, and is designed to be adjustable so that it can be tightened or loosened as needed to suit the conditions. The size of the stay, in this case 660mm, refers to the length of the stay, and the model number A150 may be used to identify the specific type of stay being used. Heavy Duty and 16mm may refer to the strength or durability of the stay, and Coastal may refer to the location or environment in which the stay is intended to be used. It is important to follow the manufacturer's instructions for the proper use and maintenance of the stay, as well as any safety precautions that may be necessary when working with the equipment.