Sorbo squeegee channels are extruded from high quality aluminum alloy. As a result, they're extraordinarily rigid and strong, but light. Thus, allowing them to be manufactured in lengths previously deemed impossible. An 18" channel weighs only 4.8 ozs (.13 kg) Being rigid they apply pressure evenly from end to end, assuring streak free windows. Longer lengths enable you to cover a larger area in less time. To ensure compatiblity please order Sorbo handles and rubbers only.