The inside gasket of the tire chucks are very tight to make sure there is a good seal. If the chuck doesn't hold or needs to be replaced for a different chuck, we do not have different size tire chucks. It's a standard size and that chuck is used in all of our hand inflators and most of our combination jump-starters. If you cannot get your tire chuck to stay on you would need to return the unit or send it to a service center for replacement.