These Pyrex® open ended cylinders are designed for use in the Disinfectant Testing Procedure as described in the 1992 J.A.O.A.C. Hard Surface Carrier Test for Efficacy Testing of Disinfectants: Collaborative Study. Made of sturdy borosilicate glass, they can substitute for stainless steel cylinders in the test. Tubes are glazed on both open ends to remove sharp edges. Nonsterile. Reusable.