Round Bottom Headspace Vials. caps Two sizes: 23 x 75 and 23 x 46 mm Round bottom glass headspace vials feature a 20 mm beveled crimp top that creates a much tighter seal than you get with a flat crimp surface. Vials are designed for use with Perkin-Elmer, Tekmar and Varian. Vials are heat annealed to 530°C.