Cleans flues and other boiler parts without scratching or damaging the material. Easily removes stubborn dirt and deposits, and helps extend the service life of any boiler. Also useful for miscellaneous cleaning tasks around the home, garage and workshop. Sizes 15mm dia, 50mm dia and 50 x 16mm dia. Cleans flues and other boiler parts without scratching or damaging the material. Easily removes stubborn dirt and deposits, and helps extend the service life of any boiler. Also useful for miscellaneous cleaning tasks around the home, garage and workshop. Sizes 15mm dia, 50mm dia and 50 x 16mm dia.