We offer Genuine Samson “Red Spot” sash cord in trade size #8 and #7. Samson Cordage has been manufacturing sash cord and rope for over 130 years and their Samson Slaying the Lion trademark is the oldest trademark in the country. Sash cord is preferred for existing pulleys with concave wheels designed specifically for cord. It is a fool’s errand to try to economize with the sash cord you choose. Experienced builders know to look for the trademark “Red Spot” woven right into the cord.
Pro Tip: a good rule of thumb for the amount of cord needed for re-roping a typical double hung residential window is 20′ per opening.