Some of you may have come across these rings. They are sold at sewing shops and are known to be used a sling rings by Indonesians. Indeed, in encouraging DIY ring sling (a more affordable choice to many), I did help people buy these rings, too. They are very affordable at RM5 per pair. Still great for those new to babywearing and wishing to try out ring sling options but certainly not for long-term use.
Though I have cautioned people of the possibility of them breaking, there is now one confirmed incident that a ring did break! This is why we do not encourage the use of anything that is has an obvious joint (if you have not seen one of these... they DO NOT have an obvious joint and are known to be used for slings!)!
If this can break, NEVER use craft rings... or curtain rings... or rattan rings...
While what you see in the picture will still be a much more afforadable option, especially if you are just trying out wearing a baby, if you are keen, you should just get Sling Rings (http://www.slingrings.com/). Sling Rings has been tried and tested for safety and Peekaroobaby is now carrying them on behalf of Malaysian Babywearers.