Are these safe to use in the cage? Does anyone of you use them?
The shape seems safe but I am not sure about the materials used. With all the metals and alloys and coatings I am always confused on what is safe and what is not

The ad says "Material: Zinc metal alloy(Lead and nickel free)"
http://www.amazon.co.uk/Lobster-Detachable-Swivel-Clasps-Blanks/dp/B0088MRC4O/ref=pd_sim_diy_3?ie=UTF8&refRID=03ATPBKP71XED27F9ADF

I use clips similar to these. Excessive zinc isn't good for birds, but my guys don't chew on the clips so it's not an issue. If your birds like to gnaw on the clips it might be desirable to look for an alternative, but zinc coating is used a lot and it's hard to avoid it.