Ed B wrote:
Perhaps I'm just being a **** and the thing really should fit, but
I
spent a good half hour last night trying to screw it on without
cross
threading it. When screwed on as hard as possible it still squirts
everywhere, suggesting the plastic bit is too big for the tap I
have.

Will try again tonight and perhaps take some pix

cheers all

OK, I reckon if it screws on smoothly and doesn't fall off, even when
the water's turned on, it must -- as somebody's already said -- be a
poor seal, not the wrong size. That's most likely caused by the lack
of a washer: they can jump out and run away when one isn't looking.
Just possibly, I suppose, this particular fitting may be too deep to
screw up snugly to the mouth of this particular tap: an extra washer
or two should cure that; but it doesn't seem likely to me.

--
Mike.