My custom vertical 3x5" notebook. The rings open like a binder so that you can add or remove pages easily. It just uses standard index cards that I hole punched. : r notebooks Amazon.com : Oxford Index Card Binder with Dividers, 3" x 5", Color Will Vary, 50 Cards,1 Binder (73570),Assorted (Blue, Green, Red) : Office Products MANO Wallet Credit Card ID Hard Case Holder Organizer Full Size (holds up to 20 Cards) Pink Silk Etsy Index Card Binder, 3x5 Lined Index Cards with Ring Holder and Dividers, Mini Binder, Index Cards with Ring, Small Organized Folder for Recipes, Card 3x5 Index Card Binder Clear Plastic Index Card Holder Book 40 Page Binder For 3x5 Cards, Holds 160 Cards, Waterproof & Tear Resistant Double Layer Cowhide Synthetic Leather Business Card Holder Wallet with 24 Transparent Slots Casual Business Card Organizer with Snap Closure