The black merkur SR compass measures 4 3/4"(card diameter) and weighs 4.5 lbs. The Merkur SR Compass is manufactured in Germany by C. Plath and features a full spherical construction with an internal gimbal system which accommodates all angles of heel without compromising accuracy. And, the oscillation-free double bottom compensates for volumetric changes. The black housing is seawater resistant and made of a light alloy and the super-strong glass dome is insensitive to ultraviolet rays and is guaranteed for life against cracking, crazing and yellowing under normal use. The accuracy of indication, lag error, and oscillation period all exceed the International Organization of Standards norm. Additionally, the vibration resistance exceeds requirements of BSH (German Hydrographic Institute).Other features include: red glare-free illumination, concave card with clear 5 degree graduation, 3 lubber lines, for horizontal flush surface mounting or bracket mounting, accuracy of indication is less than or equal to 1 degree, lag error is less than or equal to 2 degrees, oscillation period is greater than or equal to 4.7 sec, temperature range is -22 degrees F to 158 degrees F. Three year warranty on body.