This amazing material comes from Indonesia.  It is discovered in some rotted trees buried in volcanic ash.  A million years of elements and pressure producing this amazing find.  All these rings are designed on a saddle band (think English riding saddle wide and smooth on top and narrow band underneath.  Unless you have a nice size hand I would suggest wearing on middle or forefinger.  A) 1 3/4''long x 3/4"wide; B) 1 1/2"long x 1"wide; C) 1 1/2"long x 7/8"wide; D) 1 1/4"long x 3/4"wide; E) 1 1/2"long x 1"wide F) 1 5/8"long x 3/4"wide.