This spectroscope has been designed to let the user look through a slit spectrum of light decomposed by an optical system. The resulting spectra as viewed through the grating introduces students to many properties of visible light and optics. Allows students to quickly identify constituent wavelengths of visible light in many sources. An adjustable thin slit cap rotates to produce diffraction patterns in the desired direction. Pack of 24. Each spectroscope measures 10.25" long. Body has a diameter of 1", and ends have a diameter of 1.15"