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

Specs:

Teeth: 25/31

4.11 Gear Ratio: Low 3.31 High 5.10

4.12 Gear Ratio: Low 3.32 High 5.11

4.57 Gear Ratio: Low 3.69 High 5.67

4.86 Gear Ratio: Low 3.92 High 6.03

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