We've used it before. It's exactly what RLGA says, a transparent fire rated wall. It's really expensive stuff, at least $250 per square foot of glass, plus the steel frame.
I had a client who insisted on an all-transparent wall for the study lounge off the corridor in a student dorm in a ski resort area, so we could exceed the 25% max. openings rule. The first time some student breaks the glazing with their skis or snowboard, whoo boy, that's gonna be some repair bill! I tried to break it up with mullions, etc. to limit the extent of replacement.
I had another commercial client with some very expensive beach-area real estate, an office building with a property line exterior wall. We used the Firelite II glazing on the property line wall to give the tenants a view of the harbor. Expensive, but worth it in terms of the extra rent he could collect for the harbor view.
