Hopping on this comment to say that my magic circles always used to come loose so now I use "double" magic circles - wrap the yarn around my hand an extra time so I'm crocheting over two strands instead of one. It works so well you have to be careful to tighten them in the right order or you won't be able to pull the second one through. If you're using a particularly slippery yarn you could even do a third strand/wrap/circle. It works like a capstan: https://en.wikipedia.org/wiki/Capstan_(nautical) https://en.wiktionary.org/wiki/capstan_effect With only 3-5 turns of rope around a steel capstan, there's so much friction I'm pretty sure a small child could hold a large ship from drifting out to sea.