twenty dollars worth of weed. amounts can vary depending on quality but is usually about a gram. Smallest amount usually available in most areas, you can tell if someone doesn't know what they are doing if they ask for a dime or nickle. a 20 sack is the perfect amount to roll a nice blunt with if you know how to roll.
someone got it wrong... in case u aint never slanged, a 20 sack is 9 grams in weed, if u are dealing with an individual who knows very little about the weight of weed, you usually sell a 20 sack at 7 or 7.5 grams.