The message
from Chris Bacon contains these words:

Has anyone used them, if so are they reasonably robust What's the
internal diameter??

I've got one. It's ... OK. Mine's holding up the washing line for the
time beind 'cos I'm still moving things round the garden. It screwed
down into the soil easily, but since it's right by the path it's screwed
into gravel/sand. When it hit the clay it stopped dead and in effect
stripped the threads in the sand. I suspect if I were to try harder it'd
be OK.

Despite all that, it's holding up the pole adequately.

Diameter, they supply collars that shrink it down in steps from a
maxiumum of 60mm.

--
Skipweasel
Pay no attention to that man behind the curtain.