Abstract Stoppers are a known source of particulate contamination. This is, in part, due to various physical and technological limitations inherent to the stopper manufacturing process. As a quantitative control measure, stopper manufacturers perform a battery of release tests to determine lot acceptability against established quality standards. Among the universally required release tests is particulate load of a representative sample. Elastomer stoppers are commonly tested under guidance provided through ISO 8871-3. During BioPhorum engagement with several stopper suppliers, it became apparent that multiple elements of this particle count method — including, but not limited to, equipment, environment, and particle classification — varied across the different suppliers. Consequently, the BioPhorum Stopper Quality team determined a need to undertake a comparative analysis of the test methods and constituent variables that are currently utilized by stopper manufacturers. This paper is intended to highlight testing inconsistencies and drive the collaborative development of a more sensitive, harmonized particle count method.