This is a replacement Arrma Differential Gear Set. 

Features:

• Super-tough and durable steel to withstand extreme RC action
• Precision manufactured Gear Teeth for consistent performance in all conditions
• Metal Cross Shafts for long-lasting durability and super-efficient running at high speeds

Includes:

• (4) 10T Satellite Gears
• (2) Metal Cross Shafts
• (2) 20T Planetary Gears
• (4) Satellite Gear Shims
• (4) Metal Cross Shaft Insert