The dimensions and masses are the same for the Standard Rotary Motion Sensor and the Go Direct Rotary Motion Sensor. The measurements are as follows:

Diameter of small groove: 10 mm
Diameter of medium groove: 29 mm
Diameter of large groove: 48 mm
Diameter of outer: 52 mm
Diameter of outer with rubber O-ring installed: 55 mm

Moment of Inertia for 3-step pulley: approx. 2.7 X 10^-6 kg m^2. The mass is 8.6 g.
Moment of Inertia for shaft and encoder: approx. 1.1 X 10^-6 kg m^2. The mass is 18.8 g.

See also:
What are the moments of inertia of the disks included in the Rotary Motion Accessory Kit?
Go Direct Rotary Motion Troubleshooting and FAQs