The closure mechanism on this crossbody bag is a zipper. The material of choice for this bag is polyester.
From Nike
Nike Premium Cross-Body Bag (4L) - Black - Polyester - ONE SIZE
Foot Locker
Nike Cross Body - Unisex Bags - Black - One Size
BSTN
Nike Elemental Premium Crossbody Bag men Messenger & Crossbody Bags black in size:ONE SIZE
JD Sports
Nike Elemental Premium Crossbody Bag - BLACK - One Size