Pens normally come with 4 corner stabilizers, which is adequate for smaller breeds and/or smaller litters. If you have a medium to large breed or have more than a few puppies, consider adding 8 extra corner stabilizers (2 Value Packs). You will place four of these along the floor and four at the corners dividing the play and potty areas. This will give your pen additional stability. I consider this essential for my boxers because they are rambunctious. Although they cannot break the RoverPet, occasionally they are able to pop the straight stabilizers off when they are playing hard if we don't have additional stabilization.
The Stabilizer is made out of heavy duty industrial strength PVC. Dishwasher safe.