True confession right up front - I love circular needles. I choose them over straight needles every time. But I don't like the interchangeable sets. They come with either metal, wood, or acrylic tips, and to be honest, I can't be limited by one over the other. Some yarns just behave better on wood needles, some behave better on metal. I need more choices.
I first discovered circular needles when I brought knitting on a plane. I as working on a hat with double points and lost a needle somewhere under the seat between my seat mate and myself in our confined coach section. I couldn't retrieve it until she woke up, when we landed 3 hours later. I was stuck, and couldn't knit for the rest of the flight. A circular needle comes with it's own safety line - hanging onto the other needle on the other end.
To date, I have about 100 circular needles in sizes from US2 (2.75mm) to US13 (9mm) in lengths from 8-inches (20.5cm) to 52-inches (132 cm). Keeping them organized is a challenge.
I tried keeping them in zip up sleeves inside 3-ring binders but that was a mess. I tried coiling them up and keeping them in large envelopes - in numerical order. And while that worked, it kept the needles curled and more difficult to work with.
Straightening out the cord between the two needles is a must to make working with circular needles easier. When I first get them home, I like to hold them over a pot of steaming water to soften the curl. Then I decided that I needed a hanging holder that would keep the needles from staying coiled up.
I took a ride to Traditions by Pamela Kline in Claverack NY to see what kind of fabrics were in the outlet. I only needed a few yards. Then got to sewing layers of them, leaving slots to pass the circular needles through. I figured why not add atop narrow layer to hold double points as well.
I've since seen some handmade hanging circular needle holders for sale on etsy. as you can imagine, some are much nicer than others. this one by buttermilk cottage is quite nice.
But anyone with a sewing machine can whip one up in just an afternoon. Remember that each layer gets attached by a horizontal row of stitches that runs from edge to edge of the top most layer of fabric only. That creates tunnels in each layer to hang the needles through.