Knitting Thimbles

I have never heard of Knitting Thimbles before and now I find that there are two different kinds of them! I think--from the pictures I've seen--that they're meant to assist one in knitting with multiple strands of yarn. The one pictured to the left is the Inox Norwegian Knitting Thimble, with two thread guides (it looks like one long piece of wire wrapped to form a ring, with the ends looped to make the yarn guides), and is $3.20 plus S/H; the one to the right is the Inox 4 Yarn Knitting Thimble and is $5.00 plus S/H, and looks my thimbly to me. Both are available through Sealed With a Kiss Yarn Shop and a few other places. I imagine local knitting shops would have them, too.