The NL-4 is a traditional plated design. However, unlike standard designs, the NL-4 has raised diamond coated structures.
It is the edges of these raised diamond structures that are doing the heavy work.
The NL-4 sports an arrow-rake pattern for heavy material removal. The long straight edges cut very well across stones. The spaces in between the ridges allow for slurry to move through and keeps the surface from gunking up.
Do not use this lapping plate for sintered ceramics or diamond resin stones.