About This QUALITY MATERIALS - Durable polymer construction designed for professional use. Flexible yet built to prevent snagging and cracking. Great for business proposals, reports, menus, and other binding projects. PRE-CUT COILS - Each TruBind coil is 12 inches long and fits a letter-sized book, document, or binding project perfectly. Coils have plenty of excess length, for crimping the ends for a professional, finished presentation. PRE-SIZED COILS - 38mm (1-1/2 in.) diameter to bind up to 330 sheets of standard 20# copy paper. Maximum binding capacity of 1-3/8 inches in thickness. Perfect for most office projects. 4:1 PITCH - 48 loops per 12 inch coil. 4:1 pitch matches the 4 holes per inch punching pattern on your document / project. UNIVERSAL COMPATIBILITY - Recommended for use with TruBind Spiral Binding Machines like the TB-S20, TB-S20A, or TB-S20AP. Also compatible with other 4:1 coil-binding machines.