Has anyone tried one of these gizmos?

It was recommended to me the other day by a kitchen fitter; he reckons
these are the mutt's nuts for achieving a perfect finish/seal using
silicone sealant round a bath or back of a worktop (well, it would need
to be at 10 quid a pop!). Apparently it's made of a special material
which repels the silicone or something so there's no mess or residue?

http://www.plumbworld.co.uk/410-13327

Am quite tempted to give it a whirl but wondered if anyone else would
recommend it.

David