First, TAll BLUE BOOT disclaimer -NOT the boot for sale.  Photo is of Le C's Cabourg boot which is designed for urban wear - lighter weight rubber, funky 'suction cups' on the bottom to grip smooth surfaces like polished lobbies (and saved from landing on mine countless times), comes rolled up in a satin travel drawstring pouch and held together with a thick natural rubber band. Basically - toss in a gym bag/car trunk/locker/desk drawer and you are set - soles do make them a bit heavier, no arch support so running larger makes it easy to add an arch support or a squishy liner. I've stalked this boot on Amazon for best price and gave several pair as gifts over the years (very fond of the blue, but also bought plummy 'raisin' and green.) Bottom colors vary depends on country, but those on US Amazon tend to be black or a more translucent dark/blackish teal. They are a solid 4 for me simply because they are not for big-ankle folks and are a bit of a pain to remove due to calf fit/air suction (still love their travel style.) Btw - they fit true to size but a tad big. I do wish seller would correct photo to avoid confusion.

Now, the black boot is the right one and it does run about 1/2 size bigger, perfect for a nice thick sock. I own this one too and just came back to buy one as a gift since her size just droped in price. For Amazon newbies - prices fluctuate wildly and if Prime member has an option to get free returns and price is the same for possible sizes, get both now and return unused pair - your purchase may trigger price increase soon after ;)  as for the boot, it will last for ever with proper care. Great for running errands, gardening, etc. If you get one with a bit of white haze, it's called 'crazing' and not a defect, but how pure natural rubber behaves. It's removed by applying a thin layer of silicone which you should do to all natural rubber boots anyway once a year to keep them as new. Great little boot and an excellent value.