Unhappy buyer .What to do ???

Thanks guys.My gutt told me the same thing ,but just wanted to make sure i was thinking right.I sent him a reply back and politely told him that i dont think i owe him any $$ adjustment.Please keep in mind the man was not rude or demanding to me in his pm ,so i treated him the same.He even told me that i accurately described it ,but the problem was not seen by a visual inspection (basically thats how he said it )...