Must admit, when I saw it in the garden centre, I thought it was a ploy to create a product that they could charge a premium price for.
But when you think of all the pallets of compost that get transported round the country, cutting that to one third the weight would be better for the environment.
Apparently, it's peat free and it's the coir in it that expands, like those Jiffy plug discs and they expand A LOT so it could easily go to 3 times the size.
But I think the product is aimed at balcony gardeners who haven't got much space to store bags of compost and maybe struggle lifting them too and so could be useful for some. But I wont be buying it.