GAUGE MARKERS, 1 BLACK DIAMOND ON WHITE BACKGROUND, 400 PIECES, TRVIEWX. 1 black diamond on a white background gauge markers for TRViewX non-contact video extensometers and width sensors. These gauge markers are suitable for flat light plastic and flat light metal specimens with 20 mm or below gauge length or for width measurements, have a temperature range of -20 to 150?C, and include 400 pieces..