This is the original Leica Super Elmar M 21mm f/3.4 ASPH lens (on the left) and the new redesigned version (on the right). The new version is about 1.8 1/8 oz (50 3.5 g.) heavier at 9.75 Oz (275 g).
All owners who initially purchased this lens were asked to return it back to Leica Camera AG for a replacement, but as you can see from the picture, there are still some copies floating around that will never be replaced.
