The Halogens Gases & Vapors BTIS B (PN: 256) is qualitative (yes/no) colorimetric indicator for the saturation and end-of-service life of ductless hood filters. The indicator is designed to provide real-time indication of the breakthrough of halogens gases & vapors. Weight: 0.4g (0.02oz). Dimensions: 2.8mm (0.11in), diameter: 31.8mm (1.25in).