Look at the specs on your chain box. I believe 30 is correct for most Stihl Round File, semi chisel s/b 0, but full chisel I believe is 10.
Again, check the box your chain came in, or look it up on line. Or you can just match what is on a new chain.
Again, check the box your chain came in, or look it up on line. Or you can just match what is on a new chain.