It equals 15 mils. But if you are measuring a dry ingredient by tablespoons it is not possible to give a 'weight' you should use, since that will vary according to what you are measuring (since a tablespoon is a measure of volume and grams is a measure of weight). For example a tablespoon of sugar will weigh less than a tablespoon of lead will.
Teaspoons are all different. I never use them for measuring, having a cheap set of small measuring spoons which are very precise.
It is customary.
It is a customary unit.
The opposing systems are imperial and metric, not customary. But, meters are metric.
The pound is NOT a metric unit.
It is customary.
It can be more or less. An once (customary) is bigger than a gram (metric) but a pound (customary) is smaller than a kilogram (metric).
Metric.
Metric
Metric.
It is a customary unit.
customary
A "gran" is a German measurement, it is neither customary or metric. A "gram" is a metric unit.
I'm guessing by customary, you mean imperial. if so inches are customary/imperial