It was the MEGA pack that you can get with some modifications that I saw and heard about from others, with a few tweaks in pathing from me. As with any OP they are to small to stand up to a full scale attack, but will definitely stand up to any wild monster attack. I can't be sure who adjusted the monster bunker location on it but it works real well as they come at them from both sides. Most wild monsters path right up the tips of the middle.
