Overall good quality curtains - however they are not full blackout. They are definitely "darkening" as per the title but they don't have the additional layers or thickness to be full blackout curtains.
I'd recommend them if you are happy to accept some light bleed through and want some reasonably priced yet good quality curtains.
We got 5 sets for our place to use in 4 different rooms with different levels of exposure to sunlight, and we are very pleases with how much sun these curtains block, even the grey coloured ones. They fit our windows and doora perfectly, and they're great quality for the price, compared to theore expensive alternatives we had.