1.Different bottom shape for choosing. 2.Suitable for 8-425, 9mm, 11mm snap vials. 3.Micro-Inserts are manufactured of clear glass. Features. Micro insert vials, when used in conjunction with autosampler vials, allow for maximum sample recovery and easier sample removal because the conical shape decreases the surface area inside the vial.Micro insert vials can be used with screw tops, crimp tops, or snap top vials.