The BT240S series Laser Cutting Heads are released based on the BT240 from Switzerland RAYTOOLS AG in 2017, which are suitable for medium and high power fiber lasers in industrial applications. Compared to the BT240 series, the upgraded version of BT240S series in dust-proof design and customer experience are made a comprehensive optimization. As we all know, collimation lens is very likely to be contaminated when inserting or removing optical fibers,so the BT240S series are avoided this risk by adding an top protective window to the collimation assembly. At the same time, the bottom protective window structure is also fully upgraded, we add a dust cover on it. Double protection design enhance the user experience in the replacement of protective window greatly, and the lens contamination risk is almost zero.