Do those freezer mats work?

[MissisBoot]

I've defrosted the freezer this morning and was wondering if those freezer mats that you put in to stop it freezing up again actually work.

Does anyone know?

Hi
If you find out anything about these, or have gone ahead and bought some, I would love to know if they work as I could really do with some myself, but not hasty to waste my money. Thanks.

I only found ones that go in the freezer compartment rather than the seperate freezer section so didn't bother.