Shop › Right Angle, Hollow Shaft Helical, Gearbox OPP97-18.96 Image 1 of 1 Right Angle, Hollow Shaft Helical, Gearbox OPP97-18.96 $2,195.00 20HP. Includes backstop.Bore Size: 2-15/16”Ratio: 18.96:1Different sizes available. Please send an email upon ordering. Quantity: Add To Cart Added! 20HP. Includes backstop.Bore Size: 2-15/16”Ratio: 18.96:1Different sizes available. Please send an email upon ordering.