When to switch to a layer feed?

[GC-Raptor]

when do I start using chick grit? My chicks are four weeks old.

Right now is good. Like PachecoPeeps said and when they are outside with access to grass and bugs.
My chicks got nothing but Chick Starter feed for eight weeks, but I put them outside at five weeks and that's when I offered it to them in a separate container.
Anytime after two weeks of age can be offered, (some offer earlier) just watch to make sure they don't overdo it. GC