One-piece 7-foot belt assembly for LiftMaster and Chamberlain belt-drive openers, part number 41A35893. When the belt gets old, the teeth wear down or the belt stretches, and the opener starts slipping or skipping during travel. This is the fix for that. It's sized for 7-foot door height, so don't use it on an 8 or 10-foot setup. Belt-drive openers are quieter than chain drives but the belt is a wear item that eventually needs replacing. Cross-check your opener model and rail type against this part number to make sure it's the right fit.