definitions/attachables/chainmail_helmet.json

{
  "format_version": "1.8.0",
  "minecraft:attachable": {
    "description": {
      "identifier": "minecraft:chainmail_helmet",
      "materials": {
        "default": "armor",
        "enchanted": "armor_enchanted"
      },
      "textures": {
        "default": "textures/models/armor/chain_1",
        "enchanted": "textures/misc/enchanted_actor_glint"
      },
      "geometry": {
        "default": "geometry.humanoid.armor.helmet"
      },
      "scripts": {
        "parent_setup": "variable.helmet_layer_visible = 0.0;"
      },
      "render_controllers": [ "controller.render.armor" ]
    }
  }
}