Rack Labels: Magnetic Warehouse Labels for Racks - Camcode
Amazon.com : Pack of 25 - Pallet Rack Sign Holder with Two Magnetic Strips, Vinyl Pouch Label Holder with Side Opening, Rack & Shelf Card Holders, Size 3-1/2" Height x 5-1/2" Wide :
Warehouse Rack Labels and Inventory Labeling Solutions - Camcode