It is a type of material that stretches and is used especially for making clothes fit tightly.
Flexfit 6511 - 6-Panel Trucker Cap
Flexfit 6210 - Premium Fitted Cap
Flexfit FF6477 - Wool Blend
Flexfit 5001 - 6-Panel Structured Mid-Profile Cotton Twill Cap
Flexfit 6477 - Wooly Blend 6-Panel Cap
Fruit of the Loom 82300 - 12 oz. Supercotton™ 70/30 Fleece Crew
Flexfit 6377 - Brushed 6-Panel Cap
Flexfit ATB101 - for Team 365 Pro Performance Contrast Eyelets Cap