Your letter of __________(date) complaining about our products supplied to your order No. _________________has caused us a good deal of concern. We are nevertheless very glad that you brought the matter to our notice.
We ourselves have since tested a number of our product categories from the production batch you refer to and agree that they are not perfect. The defects have been traced to a fault in one of the machines and this has now been put right.
We are arranging to send you___________________ to replace the unsold balance of ___________________. Please return the latter to us, carriage forward. The extra ___________________we are sending you without charge will enable you to provide free replacement of any _____________ (item) about which you may receive complaints.