The pack of 5 Hozelock 4LPH drippers are suitable for connecting into 4mm in-line. They are pressure compensating and therefore will deliver 4 litres of water per hour regardless of their position within the system. They will automatically shut off when pressure is lower than 1 bar, but work best when pressure is at 1.5 bar. Use a pressure regulator to maintain this pressure throughout the system. These drippers feature an inbuilt filter and will automatically self-clean meaning that disruption to the system is kept to a minimum. They are ideal for use in hanging baskets, pots, containers and growbags and a variety of other garden locations and will deliver water directly to the base of a plant where it is most needed. To activate your product guarantee, please register the purchase on Hozelocks website.