The Gilmour Spray Doc wheel pump 4-gallon sprayer pressurizes as you walk or roll it back and forth. This point-and-shoot sprayer requires no hand pumping or heavy lifting. The unique wheel pump apparatus pressurizes the contents as you push the sprayer back and forth. Use the built-in pressure relief valve to depressurize the sprayer upon completion of your job. The unit has an extra-wide 4-1/4-inch mouth opening for quick filling, an easy-to-clean filter, and a drain at the bottom of the unit. It also features a flexible, 16-inch rotating polymer wand with an adjustable polymer nozzle and a 72-inch premium PVC hose.