So just put this in the product description. You can do this in seconds with a script. Your site developer will be able to do this for you. But... Does it really cost £8 to put a packet of bolts in bag and send via RM? Your postage costs may well be losing you a lot of sales. Ebay has 200 bags for £13 and free postage. RM cost will be under £1.40. You could sell a lot more if you have more accurate postage. Even using the word carriage will confuse people. Shipping or postage is more understood.