Simply stated, extra bold K-Cups contain more coffee. However, many extra bold coffees are dark roasted, and this roasting profile also contributes to the bolder character of these coffees.
The filter system used in extra bold K Cups is different than the filter used in the regular K-Cup. Consequently, extra bold K Cups can be packaged with about 9 grams of coffee versus 7 grams in regular KCups — a difference of about 20% more coffee.
Green Mountain Coffee is also creating new lines of of K-Cups that contain more coffee. The recent Brew-Over-Ice and Travel Mug lines of K Cups both hold more coffee than traditional K-Cups.