The Super bucking has a narrow entrance for more accurate shooting styles. The new Super Silicone version features the same design aspects of the "Super" line of hopup rubbers, but now made with silicone for improved performance.Recommended hardness / FPS combinations:50 degree: Up to 360 FPS60 degree: 295-390 FPS70 degree: 360-460 FPS75 degree: 425-490 FPS80 degree: 490 FPS and Up