1" (one inch) Screw Post extensions. 20 pieces per package. Our screw post and screw post extensions are manufactured from a resilient aluminum. The screw posts are used to fit our pressboard binders, for a replacement to the fold over metal fasteners and for some of our screw post binders. The extensions are most important for our screw post binders that have the screw post riveted to the binder. This is if extra length is needed.