Compatible Models: Designed specifically for Aprilaire humidifier models in the 600 series: 600, 600A, 600M, 500, 500A, 500M, 550, and 560. Not compatible with other models. Please confirm your humidifier model before ordering to ensure a fit. Reliable Function: The 4223 Drain Spud securely connects your replacement filter (model 500) to the bottom of your humidifier and links it to a 1/2 inch drain hose. This connection helps maintain peak humidifier performance and supports a comfortable, wellbalanced home environment. Quality: Constructed from grade ABS plastic for durability and long life. Features a strong, resilient structure with toughness, resistant to cracking and aging. Odor material ensures clean operation without unpleasant smells. Easy Installation: Simply remove your old 550 drain spud. Clip the 4223 Drain Spud into the original position. No special tools required, allowing quick setup and restoration of full humidifier functionality. Practical Applications: Ideal for homeowners looking to restore moisture control during dry winter months, helping reduce static electricity and dry skin discomfort. Suitable for maintaining healthy humidity levels to protect wooden furniture and musical instruments from cracking or warping. A reliable solution for households aiming to keep indoor air fresh and comfortable for family members, plants, and pets. By ensuring proper connection between your filter and drain system, the 4223 Drain Spud plays a critical role in keeping your humidifier efficient, dependable, and ready to deliver consistent comfort yearround.