Winters Quick Change Gears are constructed from SAE 8620 Steel, Crown Cut, 1-3/8" Wide. 

Specs:

Teeth: 21/21

4.11 Gear Ratio: Low 4.11 High 4.11

4.12 Gear Ratio: Low 4.12 High 4.12

4.57 Gear Ratio: Low 4.57 High 4.57

4.86 Gear Ratio: Low 4.86 High 4.86

To see other gear sets available, check out the Winters Quick Change Gear Chart