What's in the box:

Lixada Bicycle Rear Derailleur Pulley 12T MTB Road Bike Rear Derailleur Pulley Roller Bearing Jockey Wheel Bicycle Parts (Red)

This rear derailleur pulley is made of 6061 aluminum alloy, designed to reduce friction and increase stiffness. The steel bearing with rubber dust seal is for long-term use. And the CNC aluminum construction embraces corrosion resistance.

Features:
High-tensile steel bearing with ceramic dust seal and CNC aluminum alloy wheel.
Reduce friction, increase stiffness, enhance durability, for long use.
Used on rear derailleur for chain transportation and speed changing.
A replaceable 4mm bushing is included. (the 5mm one is configured)
Please refer to the size carefully before you buy it.
A necessary accessory for your bicycle.

Specifications:
Color: Black / Red (Optional)
Model: 12T
Thickness: 8.4mm / 0.3in
Outer diameter: 50mm / 1.9in
Hole diameter: 6mm / 0.1in
Configured Bushing diameter: 5mm / 0.1in
Bushing diameter: 4mm / 0.1in
Package size: Approx. 10 * 7 * 1cm / 3.9 * 2.8 * 0.4in
Package weight: Approx. 14g / 0.4oz

Package List:
1 * Rear Derailleur Pulley