The new GMG lids have ridges down the left and right sides that I assume are to stiffen the lid.  Are the lids a thinner gauge metal?  My lid is pretty heavy and doesn't flex much.  I just wonder why they added the ridges.

 Just ask GMG.

The guy at the BBQ store told me the grills lids are still 13 gauge and he did not know why they added the ridges.  Sorry, no help.