These are basic little girl tights, of exactly the sort you need to keep little legs warm when your little girl is wearing a dress.  The brand name, if you're comparison shopping, is "Luvable Friends". The tights look very normal:  medium quality, medium thickness nylon tights with a predictable pink color that matches all the other pink stuff in the market and as plain and versatile a white as you could wish for.  They are machine wash warm, just like you would expect.

The sizing is a little odd, though. Out of the package, the 0-9 months size is 15 inches long (unstretched) from the waistband to the tip of the toes. They claim that this will fit babies as small as five pounds and 18 inches in height. I think it will fit better starting at about 10 pounds.

The sizing on the package says:

Small: fits a baby 0 to 9 months, 5 to 18 pounds, 18 to 26 inches tall
Medium: 9 to 18 months, 18 to 26 pounds, 26 to 31 inches tall
Large: 18 to 24 months, 23 to 33 pounds, 31 to 36 inches tall
Extra-large: 2 to 4 years, 28 to 38 pounds, 33 to 38 inches tall