Helps prevent determined foxes and other predators raising the coop door. -Innovative self-locking mechanism – 100% recycled tough & durable plastic – Strong aluminium door -Once the door is fully lowered the wings are automatically released to lock it in place. You don’t need to do anything, except relax. -– Door Size: 25cm x 30cm/10 x 12inch – Runner Length: 59.5cm/23.5inch.