This valve uses a glass plug (as an alternative to PTFE or CTFE) for applications where the "out-gassing" plug material is undesirable. Designed with a precision external thread for fine control. This valve can be used as a bleed up to 1/2 turn. Full open position is at 1-1/2 turns. All plugs are totally interchangeable with other HI-VAC® counterparts and are supplied with FKM o-rings. Manufactured from 33 expansion, low extractable borosilicate glass conforming to USP Type I and ASTM E438, Type I, Class A requirements.