Bill, from my experiences with the Gok 15k & 20k is when they arrive brand new, to avoid all these various questions, grid them properly with a ruler and a carpenters pencil, and use a mellow DMT325 (Which I only just learned) and lap them until you have a clean stone. When you have that, you won't need to lap it for hundreds of razors. For an amateur like me, I won't need to touch it for a year, seriously.