If you need rainbow knee socks and habitually sort by "lowest first," make sure you check out the listing sizes, because these socks are a little different than what you're used to. You might consider something made by SD or sold by SD and made by Mod Socks or Sock it to Me, in the ~$14 range, which will be slightly thicker, a bit stretchier, and might hold up better to washing and wear-and-tear. As rainbow knee socks go, these are a 4/5, but as retro knee stockings go, they're a 5/5. The knit loops are a little bigger, you can see the row stagger where the colors change, and there are long yarn tails on the inside - not bad, but different.
If you're on a budget, not worried about a "perfect" fit, and you're willing to follow washing care instructions, these socks are a steal. I'm inclined to say they're worth the tradeoffs if you happen to fall in love with THESE particular rainbow colors, too, which is easy to imagine - they're serving "Sesame Street" in the best way, somewhere between SD's "harvest rainbow" and "radiant rainbow." The listing photos are very true to color, and the orange and yellow stripes are rather close in hue.
These are knit flat and the elastic is only carried in the 1.5" cuff, making the toe box a little too roomy for some folks, and too big or too small in the calf for some. With the right leg shape and length though, the cuff being the clingiest part will keep these up amazingly well, even when it tends to curl or the sock body tends to slouch while walking.
These are breezy and soft enough, so you might forget you're wearing them, but don't expect them to keep you warm. I bought these more for the type of sock they are than for the colors, so if you find that you love these, you might also love "Bee's Knees," "Rainbow Dreams" knees, and "Dreamy Knees."