HPLC and GC Vials, Caps, Septas and Inserts Guide 2mL HPLC Clear Vials, Screw . Part 5 Autosamper Vial Product List (Bestsellers) 1. Screw 8-425 (8mm, N8) HPLC Vial, Cap, Septa and Inserts . They are made with a 5.5 mm opening. These vials are designed