If you attach the Arc to a case, the case could be easily removed and induction charging would then be possible.
The intent is to always have your Arc attached to your phone, making it always with you when the phone is.
Should the need arise, the adhesive is made to remain sticky and can be transferred (though we don’t recommend attaching and removing the actual Arc more than 5 times). Also, flexible cases make removing the Arc easier.
Use caution when removing if attached directly to your smart phone