This T-shaped perch is compatible with HOEI holders with a 12mm diameter. The perching part is 15mm. It's a good option for those who have a holder and whose perches have been chewed. Size (approx.): 10.5cm x 6cm The holder and the bird are not included. It fits perfectly in my holder, but it seems it might be loose in some holders. In that case, please wrap tape around the base. For those who want it, we're currently offering a free 70g sample of hulled oats, which my parakeets and Java sparrows love. If you'd like it, please say "hulled oats please."