Portwest Bizweld Welding Helmet PW65Portwest Bizweld Welding Helmet with an auto darkening feature The handy auto darkening feature switches from a light to dark state when your welding begins light state is DIN 4 and dark state is adjustable from DIN 9 to DIN 13 using the external knob. Impressive response time from light to dark state in 0. 04 milliseconds; return from dark to light state in 0. 03 0. 04 seconds. Power is supplied by solar cells with 2 built in lithium batteries to