What do you call those snap shut clasp things?

[BigBoobiedBertha]

Do you know what I mean - you often have them at the top of a glasses case where you squeeze the sides to open the pouch and then when you let go they snap shut.

I have this book with a pattern for a pouch which requires one but they call them long spring clasps and all I get when googling that is the ordinary spring clasps you have on necklaces.

Any ideas what they are really called or where I might get some please?

Many thanks.

Are they these?

"Internal flex frames" it seems.

purse frames?

I noticed a craft magazine is giving one away as a freebie but cannot remember which one it is.

Ah thanks you SoupDragon - they are the ones! And the name makes more sense too - a better description than spring clasp because they aren't really clasps.

Thanks for looking GentleOtter. That website looks useful actually. I have bookmarked it for future projects.