It’s in the Stihl 2021 catalogue I picked up today at ope dealer. I asked the mechanic and he said he would look to see if he could order one, but I said wait until I have new saw $. Mechanic is super nice fella that remembers me by name. He told me he had ordered a spool of 3/8 .63 for when I needed another chain. He said only me and another guy ever asked for.63. The only reason I was looking is because of the Tsumara I got for the 661. I also found it interesting that they only had 5 gal of Stihl platinum in stock. Still no 500 on the shelf.