5-Bromo-4-Chloro-3-Indolyl b-D-Mannopyranoside, also known as X-Man, is an enzyme substrate commonly used for detecting mannosidase enzymes. Upon hydrolysis by the enzyme, it produces a blue-green colored compound that can be detected visually or measured spectrophotometrically. This substrate is useful in characterizing the activity of mannosidases involved in glycoprotein processing and quality control.