The Theory Mod Tweed Jacket features a boxy fit, round neck, long sleeves with buttoned vents, and raw tweed trim at the collar, cuffs, and hem. The Theory Mod Tweed Jacket features a boxy fit, round neck, long sleeves with buttoned vents, and raw tweed trim at the collar, cuffs, and hem. Established in 1997, New York-based Theory creates cool, expertly tailored clothing from the finest materials designed to inspire how you feel, work, and live.