In uk.d-i-y 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

I've hit a similar problem when fitting up some pressure reducers for
a greenhouse watering system.

There definitely were two different thread pitches on what should have
been the same size 3/4" BSP fittings, I've since sent the 'odd' ones
to the dustbin in the sky where all such things deserve to be.

--
Chris Green