the ivy league style was epitomized by the sack suit, which is defined as being a 3-to-2 (3 buttons with the top button "rolled" back to reveal only two usable buttons) jacket without darts and a single "hooked" vent. the pants were typically cuffed and without pleats. it was also characterized by the use of natural fabrics, shirts with button-down collars, and penny loafers. in suits, the ivy league style was promoted by clothier brooks brothers and included natural shoulder single-breasted suit jackets. in 1957 and 1958, about 70% of all suits sold were in the "ivy league" style.