Only one word for this - 'ripoff'.
A tax disc holder is a plastic wallet / pouch; sticky on one side and with a an area on the back into which the tax disc is inserted and held securely. This, by contrast, is just a circular bit of plastic. It will not stick to your windscreen and you'd be mad to trust your expensive tax disc to it.
I sent my back and got a refund - although I had to chase it. I'm amazed Amazon allow such rubbish to be sold.