I've worn lens-cover type sunglasses previously, but the fit was not correct.  When looking at the many pairs being offered on Amazon, I quickly was drawn to the sizing information given by this seller.  Out came my measuring tape and it was simple to determine which size was right for me.  They arrived quickly and ARE PERFECT!!  I love everything about them, especially the gentle, restfull tint.  I will suggest them to all my friends!