Unhappy Customer

My 5 yr old grandson is into Batman, Spiderman, Ironman you name it. He has 5 differnet costumes, however no Batman. I ordered him one and at the suggestion of the sizing chart I ordered a child large. Well it took like 4 weeks to get here, he was so excited when it arrived. The mask and cape fit fine but he would have to be about 5" taller and 30lbs heavier to fit into the costume, in fact it was to big for his 11 yr old sister. Which doesn't make sense to me, if the mask and cape fit him. Anyway he tried to hold back the tears which broke my heart. I contacted the vendor and asked what we could do. I was told since it had been opened and tried on they would not take it back. How do you know if it fits if you don't try it on ?I am throwing it in the trash along with the name of the company and purchasing him one elsewhere. I buy from Amazon several times a month but this vendor will never see another order from me.I reordered the item from another vendor and received it today, it fits him perfect and he was a VERY happy little boy. Thank you Costume Craze