Modification. Flat Bottom. Often Purchased with: Vial Storage Rack for 6, 10, or 20 mL Headspace Vials, 36 Vial Capacity, Polypropylene, ea. 20 mm Magnetic Crimp Cap w/PTFE/Silicone Septum (tan/white) with 5 mm Hole, 100-pk. 20 mm Aluminum Crimp-Top Seals and PTFE/Gray Butyl Rubber Septa, 100-pk.