Question: 8-Ball Quantity

Please excuse my ignorance but could someone please clear up this question.
Is an 8-Ball 1/8 of an ounce (3.5g) or 8 half weights (4g)?
Shamefull question I know, specially since it has been my DoC (Drug of Choice) for a while now
Cheers
Coneman

7 half weights.
3.5g
*nod*