Liftmaster 485lm OEM Battery Backup Allows you to still come & go through your garage door, when the power goes out Liftmaster 485lm battery backup system - chamberlain part number 4228- 100% omen New production dates- liftmaster factory supplied Also works with sears and home depot garage door battery back ups- replacement part Compatibility for all battery back up units with slide in battery - 3850/8550 and new models