I am building a MSI Creator X299 system, and a memory listed as compatible on MSI is CMK32GX4M4B4000C19rev4.31 This is not available, but there is CMK32GX4M4K4000C19 which only differs in the K before the speed rating 4000 instead of B. I cannot find the meaning of this letter code, and thus cannot tell if the K version should be compatible with this board. Help would be appreciated.