Concrete Perches are an excellent way to help maintain the length of toenails in your parrots, and gives each bird a hard surface to grind the beak. Only one of these perches is recommended per cage, because always sitting on such an abrasive surface could cause skin irritation, thus defeating the purpose. Since birds tend to spend most of their time on the highest perch in the cage, make the highest perch a soft perch. Place your concrete perch at mid-level in the cage, or in front of a treat/water dish.
Available in all sizes from Blue Crown Hanging Parrot (small) to Green Wing Macaw (large), also available
Polly's "Twister" (a new twist on concrete perches).