I've tried to put a stranded #12 into a Wago, just to see how it works. The result was that 1/2 the conductor went into the connector, the other half formed a "beard" outside the Wago. Hardly a timesaver. Cut it off, throw it away, restrip, try again, twisting wire with lineman's first. 3/4 in, 1/4 beard. They're junk.
