The Vevor deionized water system is designed for the final stage of car washing to help deliver a spot-free finish without hand drying. It uses 2 x 4 L of premium mixed-bed resin to remove dissolved ions such as calcium and magnesium. A built-in bypass valve lets you switch between tap water washing and filtered water for the final rinse. The included TDS meter helps monitor water quality so you know when resin replacement is needed. Its wheeled trolley base and adjustable handle height make it easy to move and use around cars, RVs, windows, and more.