ok how does this work ?

here

never heard of them before (am i showing my ignorance?)
is there any point?
how does it work ?

cheers

The innards of the valve are based on a pair of non-return (or 'check' ) valves.

When you push the brake pedal, the outlet closes and the wheel cylinders/pistons move. When you take pressure off, the inlet closes and the outlet opens, allowing the wheel cyl. piston to return and push the fluid back down a return line.

The return can be just a plain metal pipe, which allows the fluid to cool as it returns to the reservoir, or it can be piped through a cooler.

Essential kit (but not necessarily that one ) on endurance type cars, and some rally cars.

Cheers,
Syd.