300mm long stainless steel braided flexible tap tail.
15mm compression fitting on one end, 3/8 inch BSP connection on the other (unusual size, sometimes found on continental toilet cistern float valves).
The hose must not be : A-Twisted, B-Squashed, C-Stretched, D-Kinked or E-Bent sharply (especially near the ends).
BSP (British Standard Pipe Thread) sizes don’t match up with what you would measure using a ruler. Have a look at the BSPT link at the bottom of this page for more information about how plumbing threads are measured.