Size Variety Kit, Antistatic conductive vacuum cup, with a choice of 3 materials Antistatic High-Temperature SiliconeAntistatic Nitrile Buna-NUltra Pure Silicone for Optics - Photonics8-pack includes one each: 2.38,3.18,4.76,6.35,9.53,12.70,15.88,19.05 mm Diameter. SO Class 5