Fixing Kayfun 5 airy draw my way.. Remember those three little metal? It's from a lagendary tank Vivi Nova. I pick the one on the right. The inner diameter is 2mm. But the outer diameter is over 3mm which will not fit into the Kayfun 5 air channel. I then take my vise. Use a nail to hold and secure it in place. Start filing and inspect if it fit the air channel. If not, keep filing.. Once perfect.. Fixing Kayfun 5 airy draw my way.. From stock 3mm to 2mm.. I'm more than happy now!