The 3.5 gallon PRO is our first battery-pressurized model, boasting a consistent, high pressure spray. The battery pressurization is not only strong, but makes the PRO easy to use - simply pour water in the top fill cap, press the power button and spray! The PRO is perfect for avid surfers, campers, bikers and outdoor enthusiasts who want more capacity plus the consistency, strength and convenience of battery-powered pressurization.