Comparison : Item # A0507, 100 Series 1:1 (Miter) Gear Ratio, 0.75 Inch (in) Shaft Diameter, and A Rotation Gear Drive
Item # A0508, 100 Series 1:1 (Miter) Gear Ratio, 0.75 Inch (in) Shaft Diameter, and B Rotation Gear Drive
Item # A0509, 100 Series 1:1 (Miter) Gear Ratio, 0.75 Inch (in) Shaft Diameter, and C Rotation Gear Drive
Item # A0510, 100 Series 1:1 (Miter) Gear Ratio, 0.75 Inch (in) Shaft Diameter, and D Rotation Gear Drive
Item # A0511, 100 Series 1:1 (Miter) Gear Ratio, 0.75 Inch (in) Shaft Diameter, and E Rotation Gear Drive