With the exception of a "New! Twin Pack!" violator on the left bag’s corner and a "For Added Freshness" violator in the right bag’s corner, each bag features repetitive graphics and copy. For example, a total net weight appears on both bags, as does the same contact-coded use-by date. The Twin Packs were introduced nationally in May 2001 in the company’s two most popular varieties, romaine in an 11-oz Twin Pack, and an iceberg and romaine blend in a 14-oz Twin Pack. It appears that the middle seal between alternating bags remains uncut when it is produced on form/fill/seal machinery. However, Fresh Express would not detail how the packs are produced, nor identify the specific film structure. However, Sprague does acknowledge that the package structure is typical for their bagged lettuce. The same Keep-Crisp™ modified atmosphere packaging used in its single packs keeps the Twin Packs' salad fresh and preservative-free for up to 14 days under refrigeration. The packaging regulates the oxygen content within the bag to control the respiration rate and therefore the shelf life of the salad inside. Each salad blend breathes at a different rate and requires specifically formulated packaging film, Fresh Express states. Sprague explains that one of the challenges is to ensure that the packs are merchandised in fully spread form. "If folded over to save shelf space, it can confuse consumers," she says, "as they can't see or understand the benefits of the Twin Pack. Smaller bags of lettuce have proven unpopular with consumers," Sprague explains, "hence, the Twin Pack alternative." Both packs retail for $2.99.