From the manufacturer:

Venom’s Thumb Grips are designed with comfort and game play endurance in mind. The ergonomically designed textured rubber grip fits over the analogue stick on the PS3™ controller to enhance grip and ensure maximum comfort for longer game play. The Thumb Grips are easy to fit in seconds.

Key features:

•    Compatible with PS3™ and Xbox controllers

•    High-quality, professional-style textured surface

•    Simple application takes only seconds