Alkali Scientific™ 9 mm blue screw caps are packaged 100 per pack and feature a press fit, pre slit PTFE/silicone bi layer septum. This combination is widely used across a broad range of applications and is especially suited for HPLC when working with less volatile samples or when snap or crimp top vials are not appropriate. These caps are the most common closure for 2 mL vials and are fully compatible with all wide opening 2 mL glass and polypropylene vials, as well as 2 mL micro vials and High Recovery vials. While snap top vials are an alternative, Alkali Scientific™ screw caps remain the preferred choice for convenience, versatility, and reliability. Designed with a non bonded, press fit septum, these caps are also the most sustainable option—allowing components to be easily separated for proper disposal and recycling.