The Mobius camera has used different lens types since its initial release. The camera was initially released with a standard non-wide angle lens, referred to as "Lens A". This version is still available for purchase today. Subsequent to the initial release, a wide angle version was released, and was offered in addition to the non-wide angle Mobius. It is this version that has seen a change of lenses over time.
The lenses were changed several times in order to meet demand and maintain quality, all while keeping the camera affordable. The original wide angle Mobius shipped with a lens referred to as "Lens B". This is the smallest of the wide angle lenses, and also has the narrowest FoV of the wide angle lenses. This lens was subsequently replaced with wide angle "Lens C" in January 2015. Wide angle "Lens C" was very popular, in part due to lack of lens flare, and larger 131 degree field of view. However, it was subsequently replaced with "Lens C2" in July 2015 due to quality control issues. Although "Lens C2" suffers from more lens flare than its predecessor, it does have slightly better corner to corner sharpness, and a slightly wider field of view.
The photos below give a compairson of the field of view of the different lens types, as well as the physical differences between wide angle "Lens B", Lens C", and "Lens C2".