The Studica Robotics 20-Tooth GT2-6mm Timing Belt Pulley can be used with any of the GT2 belts.
The Studica Robotics 30-Tooth GT2-6mm Timing Belt Pulley can be used with any of the GT2 belts in your robotics builds.
The Studica Robotics 40-Tooth GT2-6mm Timing Belt Pulley can be used with any of the GT2 belts in your robotics builds.