COG LCDs come in various display modes, the two that are most commonly used are STNs and FSTNs. STN (super-twisted pneumatic) displays provide more contrast than TN (twisted pneumatic) displays by twisting the crystal molecules from 180° to 270°. FSTN (filtered super-twisted pneumatic) displays use a film compensating layer between the STN display and the rear polarizer. This adds sharpness and better contrast to the display.