I bought this one 2 years ago to replace expensive Optrel with a non replaceable battery. Unlike Radios, it wasn't in my capability to install a battery without breaking the cartridge. It is the same offshore one that some welding supply stores have for more $$ . I was going to get a nice Viking, but I couldn't get the fit right . Not that I can get this one to fit right either, but it was 40$ rather 300. I still have a tweaker for a back up. BTW the battery is replaceable and the lens is clear when ever it is clean! https://www.amazon.com/gp/product/B073PY7F68/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1