The TW-8E Excluder has the adapter plate screwed on. The purpose for attaching the adapter plate with screws is to provide interchangeability among holes. If you suffer SREH anxiety, or prefer trying to start a new colony with round holes, then you can use the TW-16 or a TW-16A round hole adapter plate until your birds have built nests or laid their eggs, then by removing 2 screws, switch the entrance to an Excluder. Then, apply a small amount of latex caulk to waterproof the area where the adapter meets the tunnel. The TW-8E Excluder is for larger natural gourds, or Supergourds. The TW-8E sells for $7.00 plus S&H.