7" Zipper YKK #3 Skirt & Dress Closed Bottom ~ 578 Rail Grey (12 Zippers / Pack) 7" Zipper YKK #3 Skirt & Dress ~ Closed Bottom 578 Rail Grey (12 Zippers / Pack) Strong yet lightweight zipper for slacks, skirts and dresses. These are nylon zippers with plastic teeth and a metal slider. They are ykk brand and are closed ended (non separating).