This Myson ABV22 automatic by-pass valve is a great addition to any home plumbing system. With a 22mm size, it is perfect for controlling the flow of water around your heating system without any hassle. The valve is made from high-quality materials, ensuring durability and long-lasting performance. This unit comes with one automatic by-pass valve, making it a convenient option for anyone who needs to regulate their heating system flow where all radiators may be shut off due to trv's operation this eliminates pump damage.