Description General description Sleeve stopper septa are manufactured from pure natural rubber for excellent resealability when used for cannulation techniques or from FKM rubber for high chemical resistance. Natural rubber septa are available in red and white colors and a soft rubber formulation that contains no fillers or coloring agents for super tactility and easy manipulation. Storage Note for Natural Rubber Septa: Store septa in a closed bag out of sunlight to retard blooming, which is the formation of a whitish film on the surface of the rubber. Blooming is a natural process and does not affect performance. Remove visible bloom by washing or wiping off before use.