The Seagull™ is a powerful accessory for examining powders, optical coatings, opaque substrates, films on opaque substrates, and slightly curved solids by variable angle FT-IR reflectance spectroscopy. This accessory easily adapts for specular, ATR or diffuse reflectance measurements. The Seagull™ operates over a broad range of incident angles without misaligning the system, defocusing the incident radiation, or changing polarization. This makes it an extremely versatile and flexible tool for FT-IR spectroscopy. The Seagull™ also allows changes in the incident angle without interrupting the spectrometer purge. The Seagull™ is excellent for examining solids by specular reflectance or ATR, for studying liquids and films on liquids by specular reflectance, for depth profiling, and for determining optical constants.