I wanted to just try the concept inexpensively, so l bought a battery operated one from Harbor Freight ( for saws). This one was magnetic...my machine mostly plastic, so l used velcro with sticky back. The laser worked fine, but l didn't like it sticking out where it was, and that was the only place it worked for the job. I kept getting caught up on it when threading and " flipping" sewing projects around. I did try removing it when not using it , then putting it back. In the end, when the battery died, l never bothered replacing it.