Unity - Scripting API:

public Rect(left: float, top: float, width: float, height: float)

public Rect(float left, float top, float width, float height);

Parameters

Creates a new rectangle.

	var rect = Rect (0, 0, 10, 10);

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public Rect rect = new Rect(0, 0, 10, 10);
}

public Rect(position: Vector2, size: Vector2)

public Rect(Vector2 position, Vector2 size);

position	The position of the top-left corner.
size	The width and height.

Creates a rectangle given a size and position.

This form of the constructor is convenient when you are already working with Vector2 values.