I have the feeling that the lifespan of one of those multipliers when used with an impact wrench, any impact wrench, would not be very long. Think about taking a ratchet and beating on the handle with a hammer to loosen a fastener.
Not supposed to use an impact on them. We used them when I climbed wind turbines, but not with an impact and the good ones were not cheap. However, we were using them to torque stuff so they had to be accurate. The Northern tool cheapo might be ok for disassembly, but most impacts ought to exceed it's rated capacity anyway so unless you don't have an impact it's doesn't make sense.
