This is a perch for birds. It is made for the HOEI 35 cage. Commercially available perches are easily chewed up and become tattered, but this one is made of very hard wood, so it is durable. It is safe for cockatiels. It uses wood that is safe to eat. The diameter is approximately 1.7cm to 1.9cm. The first photo shows it attached to the cage for the purpose of taking the picture. Returns and exchanges are not accepted, so please understand.