The Coupon Expires 12/14/17, The Expiration date may depend on when you print it. The print limit is two. The coupon states limit of one identical coupon per shopping trip.
Walmart sells the 18oz for $2.97. Buy three for $8.91. Use the Buy two get one free coupon above and pay $5.94 for three or $1.98 each.
Through 11/11, The Dollar General has 18oz Purex Crystals priced at $4. Buy three for $12 and use the Buy two Get one Free coupon above and pay $8 for three or $2.67 each.