This is a dryer vent elbow that is 4 inches in diameter and has a 90-degree angle. It is used to redirect the flow of air and lint from the dryer to the vent system. The elbow is made of a durable material that can withstand high temperatures and is designed to fit with a 4-inch vent pipe. The 90-degree angle allows the elbow to make a sharp turn in tight spaces, which can help to conserve space and make the installation easier. This elbow is suitable for a dryer vent system with 4-inch diameter vent pipes and needs to make a 90-degree turn.