#16 is a flat-edged brush with a small tip, 3mm across. Kevyn Aucoin's concealer brush looks very similar. IMO pointed eye brushes work better for detailed eye lining, or synthetic angled brushes for getting a fine line. Overall, #16 is just not very flat- or fine-tipped. When wet, the outer bristles can splay out, making it even less ideal to work with. This brush is becoming hard to find, probably because it's not really necessary. I'm keeping mine as part of my collection, but I don't reach for it often.