The cheap auto-darkening available everywhere; amazon, aliexpress, ebay are, according to this test with a sample size of 1, OK. There is very little difference in speed. But there are two MAJOR concerns. No ANSI certification and they are VERY dark when not triggered. In future tests I'll see how temperature affects different models and I'll test Harbor Freight's Vulcan and 3M Speedglas. Early Access to vids here http://www.Patreon.com/AvE