I have this envelope now for 1 month. I was initially very enthusiastic about it.
But now is abgrebrochen piece to the volume control the thinness. It has only just solved but then it went on my nerves and I have demolished it. I use the shell now still. She still holds good despite the lack of stucco.
It's just annoying ... but I can live with it.
Conclusion:
If you do not mind the break off a part of the shell after a few weeks, I recommend the sleeve.