The ResMed F20/F30 series of CPAP masks offer two different elbow options: the Quiet Air Elbow and the Standard Elbow. The Quiet Air Elbow is designed to reduce noise during CPAP therapy, allowing for a more peaceful sleep environment. The Standard Elbow is designed to provide a more secure fit and is suitable for most users. Both elbows are compatible with the F20/F30 series of masks, allowing users to choose the elbow that best meets their needs.