Protractor 360 Degree 4" Smoke- 0.80 thick, topaz tinted plastic which provide contrast and easy visibility. High quality protractor with beveled edges. Open center with a crossbeam that has a finger lift. Resistant to breakage and will not discolor. Imprints have sharply defined graduations in one degree increments. Used by engineers, architects, draftspersons, and in schools for geometry instruction.