This is a two part set that replaces the hangar doors on the 1/350 TOS Enterprise from Polar Lights. It is for folks that want an open hangar door, but also want to occasionally close it. Or only open it when looking at the hangar interior. It's up to you. The outer peice installs just as the open door kit part does. The inner piece slides perfectly into place to create a seamless closed door. There is even a slight lip for light blocking.