Splits one 3/4 inch BSP (standard thread size for the end of washing machine and dishwasher inlet hoses) connection into two, could be used to connect a dishwasher and washing machine or fridge to the same valve. Also useful if you only have a cold supply and your older washing machine needs hot and cold water supplies.
Brass is the metal of choice for quality plumbing fittings, this item is much stronger than the normal plastic Y splitter.
Complete with sealing washer.
Have a quick look at the BSPT section at the bottom of this page for information on British Standard Pipe Thread sizes (a 3/4 inch BSP thread measures 1 inch with a ruler).