A friction stay 400mm side hung A090 inland is a type of window hardware that is used to allow a window to be opened and closed. The friction stay is a device that helps to support the weight of the window as it is opened and closed, while the side-hung feature allows the window to be opened from the side rather than the top. The A090 inland designation may refer to the specific design or performance characteristics of the friction stay, such as its intended use in non-coastal environments. Friction stays are often used in combination with other window hardware, such as hinges and handles, to provide a smooth and reliable opening and closing mechanism for windows. The 400mm measurement may refer to the length of the friction stay or to the size of the window it is intended to be used with.