hello dear I am very sad for that. 80 grit is very close to 100 grit. if the quality is very poor and you can not use, so you just return the goods to our warehouse in USA, we refund full payment back to you. But you did not allow, the item total amount is $590. you insist on letting us refund $500. 4000pcs only value $90. this is too much for us. you return goods to warehouse in USA, we still can use the nail files. I think you return goods and we refund full payment is the best option for both of us. you can minimize your losses and so do we.