Heavy duty boxes (Clarendon Park LE2)

Need heavy duty boxes to return dumbbells need to be heavy-duty/double walled boxes able to hold 15kg,12kg 10kg and 8kg.Medium size boxes no bigger than 61cm length ,46cm Width and 46cm Height.Sending them back via Royal mail have to be right size and not weigh more 20kg.
If have four boxes be much appreciated 👏
Kind regards from Angela