Aijiren’s 20ml crimp top headspace vials have two types of round bottom and flat bottom. Please check the instrument you are using before buying. Is the round bottom or flat bottom headspace vial suitable? Aijiren designed the 20ml crimp top headspace vials in order to be more Accurately use with your instrument. 20ml crimp top headspace vial has a very good seal and can be used for volatile samples, but it needs to be used with 20mm Hand Crimper to seal the vials, and when opening the lid, it needs to be sealed with 20mm Hand Decrimper. You can refer to Aijiren’s product page to purchase the matching Hand Crimper/Decrimper.The caliber of the 20ml crimp top headspace is 20mm. Before buying, you need to check the specifications carefully to prevent it from being used after purchase.