Here our facilities and hospital has requested fabric ties only- the elastic doesn’t fit everyone and is very uncomfortable. They want to be able to tie their masks so they fit each individual. Tshirt knits, bias cut fabric and and elastic all stretch out and soon are not fitting- hot water wash & drying also degrades their usefulness. Check with who you are making them for to see what they prefer- if the masks are only used once and thrown out or if they are being laundered and reused makes a difference too.