The LiftMaster 041D0277-1 residential garage door opener transformer from Garage Door Supply Co. is engineered for use with several LiftMaster Wi-Fi battery back-up belt drive operators made after 2011. It's compatible with LiftMaster 8550W and 8557W belt drive operators and other models. To confirm compatibility, check your owner's manual or our website's illustrated diagrams that list replacement parts and part numbers for each model.Product Highlights: