First, read the English article below.

If in doubt, a standard size of 8.5 by 11 inches will do fine; you can fold and cut it in half before beginning if you want a smaller envelope. 

Now, please write a short abstract for it in Vietnamese. Abstract:
Dùng giấy có kích thước lớn gấp đôi kích thước phong bì bạn mong muốn.