Jacto HD400 4-Gal. Backpack Sprayer has an internally mounted poly piston pump that eliminates potentially dangerous leaks and produces a maximum 75 psi with only six pumps to reach 45 psi. Features an internal agitator and volume markings in gal. and liters. For extra comfort, add on the Deluxe Harness and Waist Belt, Item # . Jacto HD400 4-Gallon Backpack Sprayer