We too have a "rolling tube", about a 2 foot length of black drain pipe, 4
inches across.  And all 4 ferrets love to roll in it.  They too will try to
make it roll themselves, and as they throw themselves onto their backs, it
usually does roll, at least once.  But they look out at me, upside down,
begging to be rolled.  And as fast as one comes out, another goes in.
 
The remainder of the grooved tube is in a single length, about 8 feet long.
Besides just running through it on the floor, they like to have it held with
1 end off the floor.  I brace it against the kitchen sink and they climb up
the inside, popping out the top, and climb over the side, into the sink.  I
then lift that one to the floor, where he races back to the end and does it
over and over.  All 4 ferrets have been in the tube at once.  As soon as one
is out the top, another head appears.  I'm setting ferrets on the floor as
fast as I can!  The exercise of climbing the sloping tube is great for them.
 
Georgia
[Posted in FML issue 2218]