uxcell 2 Pcs 3.5" Dia Metal Scrapbooking Staple Book Binder Loose Leaf Rings Keychain Binder rings lock securely; made of tough metal can withstand heavy use Outside Diameter : 88mm/ 3.5"; Inside Diameter : 80mm/ 3.2";Thickness : 4mm/0.16" Durable metal will not crack , split or bend Rings open and close easily and lock for extra security; Easy to operate: pull to open and squeeze to close Ideal for fastening any size document stack and keys and swatches too!