In English, these pieces of plastic are called "Sheet Lifters", and they are put in binders so your pages don't bend. What are they called in French? : r/French
Lift plastic or laminate sheets and move them in position | TAWI
Durable Sheet Lifters, Durable Easy Flow, 11" x 3", Lifts Sheets Over Rings and Protects Sheets from Tearing, Fit Standard 3-Ring Binders, Black (20 Pack) : Amazon.co.uk: Stationery & Office Supplies
Sheet Lifters - Steel, Plastic, Glass Lifting | DAB Technology
Durable Sheet Lifters, Durable Easy Flow, 11" x 3", Lifts Sheets Over Rings and Protects Sheets from Tearing, Fit Standard 3-Ring Binders, Black (20 Pack) : Amazon.co.uk: Stationery & Office Supplies
Wilson Jones Durable Easy Flow I Sheet Lifters for Binders - W364-99 - YouTube
Steel Sheet Lifter | Plate Lifter | Bundle Lifter
Caldwell STRONG-BAC Small Bundle Sheet Lifter
Custom Slipcases & Boxes, Index Tabs, Presentation Folders, Mailers & Media Packaging: Advanced Looseleaf Technologies
Binders & Albums | ARCHIVAL PAGE LIFTERS | Archival Methods