cubepath
The edge flip: Turns the front-right edge pair over in place. Seven outer turns, nothing wide — so it cannot break a pair you have already made, and it means the same thing on a 5×5

The edge flip

Turns the front-right edge pair over in place. Seven outer turns, nothing wide — so it cannot break a pair you have already made, and it means the same thing on a 5×5

Big-cube pairing4×4

Algorithm

R U R' F R' F' R

The edge flip case diagram
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The replay starts at the case and solves it — step through it, or drag to rotate.