Optimal Safety for Your Pups: Premium PP and HDPE materials used in injection molding - sturdy and tightly connected without gaps; each wall weighs 4 lbs, providing enough weight to make it effectively self-supporting and prevent movement even when a dog leans against it; the pig rail prevents the dam from crushing pups that may get stuck between her body and the edges of the box. All are designed for absolute safety, so you can really relax without worrying about your new-born pups. Roomy Interior Space: Interior dimensions(46" x 92"); exterior dimensions(48" x 96"). Unlike narrow enclosure cage or kennel, Senneny whelping box are large enough for the mother to lie down, stretch out fully, and nurse the puppies. 2-rooms whelping box, one for cleaning, feeding the pups and providing the heat source, the other for the mother to rest and cool off where close to her babies. A Clean & Warm Environment for Pups: The unique design of raised patterned panels cleans easily with a simple rinse or wipe it with water; in addition, as pups initially cannot control their body temperature, so Senneny whelping pen provide a holder to hang the heat lamp and can keep the heat source centered in the box.