A size set is one garment in each size passed round the team so people pick their own. For any order above about fifteen people it saves more in wrong sizes than it costs in time.
Running a size set costs us nothing extra to provide, so there's no reason not to ask for one on any order where you're not certain of everyone's size. The only trade-off is a few days added to the timeline while it does the rounds — worth it against a pile of wrong-size branded stock.
The questions are free. So is the quote.