This knapsack sprayer is a type of garden sprayer that is worn on the back like a backpack. It is used to spray pesticides, herbicides, and fertilizers on plants and crops. Knapsack sprayers are available in different sizes and capacities, ranging from 5 liters to 20 liters. They are designed to be comfortable to wear for prolonged periods of time and are equipped with adjustable straps and padded backrests.