I have never been a fan of knitting needle tip protectors – how many times have you found that the force of the stitches on your needle have popped the guard off the end, or they simply fall off from the friction of being carried in a bag? I wanted a soft flexible something that would actually slide onto my needle and keep the stitches from sliding off. That's when I found Cocoknits stitch stoppers. They have cylinders made of durable, EVA foam in a variety of sizes with an opening in the middle that accommodate everything from size 0 (or the cord of an interchangeable needle set) to a US 15. Problem solved!
The original size has 4 each of 6 sizes (24 total), and accommodates needle sizes US 0-15.
The jumbo size has 4 each of 3 sizes (12 total), and accommodates needle sizes US 15-19.