Would a Shimano 105 R7000 left side crank fit on an Utegra 6800 crankset? I'm looking at getting a left side crank power meter and was wondering would the various shimano left cranks available with power meters fit with the existing Ultegra 6800 crankset I have? The 105 or even dura ace. Thanks
Yes, you can use the left crank arm of your choice from the Hollowtech II road series. (105, Ultegra, DA)
It is quite commonly done, especially using a newer generation arm on an older chainset where the older style is no longer available.