Feature: 1. INCISIVE KNIVES: Book binding machines have incisive knives, crisp holes without burrs, and carbon structured steel knives with 5,000 punch tests. 2. FIXED PAPER SLIDER: Comb binding machine adopts fixed paper slider to lock the paper size and prevent paper from overflowing in the hole. 3. CURVED FORCE ARM: Manual binding machine adopts curved force arm, which is easy and convenient, and fits the hand shape and labor saving structure. 4. ADJUSTABLE: Comb binder machine adjusts the distance between the hole and the edge of the paper by sliding the button left or right. 5. EASY TO OPERATE: 21 hole binding machine is easy to operate, easy to punch holes, binding thickness of 10‑450 pages, and durable. Specification: Item Type: Manual Binding Machine Material: ABS, Iron Binding Thickness: 10-450 Pages. Package List: 1 x Manual Binding Machine1 x Other Accessories1 x Instruction Manual