To take bearing of a point, compass is held near eye and read down line of sight. Stable bearing appears in prism in perfect focus day or night.For quick reference, a heading can be determined by looking straight down at compass and reading degree shown with magnifying lens.Contrasting black and red numbers on compass card make it quick, clear and easy to read.Compass features liquid-dampened card with photo luminescent night lighting that quickly charges by placing compass momentarily under bright light. No batteries required.Colorful, sturdy, rubber housing protects compass.Includes an integral lanyard, which serves as convenient neck or wrist strap.Lifetime warranty.Factory certified accurate to within 1 degree.Includes directions for use and numbered calibration certificate.Dims: 1-3/16" x 3-3/16" (30 x 81 mm).Weight .29 lbs. (132 g).