The attached bell is a huge mistake. Cats have sensitive hearing, and constant ringing, 24/7, with every movement, right under their ears, causes them stress and frustration. If you're buying this collar, please, I beg you, take some scissors and CUT OFF the bell before putting it on your cat.
I have several pieces, and I'm happy with them. They open easily if the cat gets the leash caught on something—actually, a bit too easily for a 5 kg cat... Personally, I would have preferred if the minimum size was a bit smaller. It slips over the cats' heads easily even when adjusted to the smallest size (not for the tomcats though, since their necks are thicker).