Make the player completly invisible

Hello, I am working on a mod called "Souls of despair" and i am working on an chestplate (a single piece of armor) "Ghost Neackle", i wanted it to make the player AND his armor completly invisible while crouching and wearing this. I could just make it give the player invisibility, but i haven't even tried because it only makes the player invisible, not the armor. I saw plenty of posts related to this, but i couldn't do anything said in them. Does someone know how to make the player completly invisible?


PS : Sorry for bad english, i'm from poland.