There are at least two sizes for these coupons depending on the size of the cereal box. The 18oz corn flakes (that I got for $1.59 at Giant in Maryland)have a very large coupon. This would affect weight/postage.

Do you have to send them in 5 at a time or can you send in 10 or 20 or whatever all together?

Anyone from the DC area might be interested to know that Giant currently has forms that offer one DC United soccer ticket with every purchase of 3 kellogs cereals through 8/12/00. I wonder when this started, maybe a can find and submit some of the $1.59 corn flakes receipts!