The Heavy series of Weight Disks has three different versions that were updated as newer Beyblades were released. Chronologically, the first Heavy WD to be released was Six Heavy, followed by Eight Heavy, and finally Ten Heavy. The number before the word “Heavy” on each WD represents the number of sides on each WD (ex. Eight Heavy would have eight sides, making in into an octagon shape).
Note: The six sided version of the Heavy WD is officially referred to as simply "Heavy", but the word "Six" is commonly used before the word among Bladers to differentiate between all three types.
As the name “Heavy” implies, the Heavy series of WDs is the heaviest available weight disk (including WDs not in the Six/Eight/Ten sided category). Due to the heavy weight and the compactness of that weight, the Heavy weight disks are often used for Compact type combos for the simple reason of increased RPM. When the weight of a Beyblade is focused towards the centre (as opposed to a Wide WD where is is focused around the perimeter), its RPM will increase. This weight is also often put to use in Defense oriented customs, with weight being the primary concern in that type. Ten Heavy is the heaviest out of all of the Heavy weight disks, and generally speaking, is chosen over Six and Eight Heavy when customizing.