three.js/src/helpers/Box3Helper.d.ts

import { Object3D } from './../core/Object3D';
import { Box3 } from './../math/Box3';
import { Color } from './../math/Color';
import { LineSegments } from './../objects/LineSegments';

export class Box3Helper {
  constructor(object?: Object3D, color?: Color);

  type: string;
  box: Box3;
}