FireUp Polypropylene Flue Brush 5" Head for Flexi Flue KitsThe PULL THROUGH brushes are designed for extra long spans of flue, or for those extra tricky kinks. Each end has a wire loop allowing rope or clip attachments so the brush can easily be pulled backwards and forwards through the flue. The Polypropylene Brush Heads are widely recommended for most flue cleaning applications. The polypropylene bristles are hard wearing, long lasting and strong. The will give you a really good clean.