What's in the box:

11T Aluminum MTB Mountain Bike Bicycle Jockey Wheel Rear Derailleur Pulley (Black)

Features:
CNC machined aluminum alloy jockey wheel with bearing center.
Super light, weighs only 11 grams.
Compatible with shimano 11 teeth rear derailleur.

Specifications:
Material: Aluminum alloy
Color: Black / Blue / Golden / Silver / Purple / Red (optional)
Inner Diameter: About 5.2mm
Weight: 11g / 0.4oz

Package List:
1 * Rear Derailleur Pulley