Since about 2014, there has been a concerted push by the USP packaging subcomittees to revise packaging-related USP test chapters, a process that is still ongoing today. Prior to their revision, many chapters incorporated antiquated test techniques and failed to consider or provide guidance on novel packaging systems, materials, and use cases. The USP <661> chapter on plastic packaging systems was one such chapter, and was subsequently heavily revised, first entering PF as <661.1> for plastic materials of construction and <661.2> for plastic packaging systems in 2013. Ten years later, with many changes and challenges along the way,  in 2024, the chapters are still not yet effective, with adoption required by December, 2025, and strongly encouraged in advance. Through this presentation, CS Analytical will review the scope and reasons for heavy revisions to the USP packaging chapters, including how those changes have played out in the case of <661.1> and <661.2>. A review of the application of these chapters will be provided, along with a historical review of the changes to the chapters since 2013, and to this day. Topics will include real-world examples of challenges in defining and implementing <661.1> and <661.2> testing, and modern approaches to overcome some. The presentation will include relevant updates to the chapter since the last webinar on this topic, held in April 2023.