Shimano Dura-Ace 7900 cranksets do not have a removable spider. Therefore Quarq a power meter spider cannot be mounted to the Shimano 7900 crank arms.
If you have a Shimano Dura-Ace 7900 crank, and wish to use a Quarq power meter, you would need to purchase a Quarq power meter chassis (power meter spider and crank arms) which takes the place of the Shimano crank arms.
Available Quarq power meter chassis' include:
- Quarq DZero Carbon
- Quarq DZero Aluminum
See the article "Dura-Ace 7900 chainring compatibility." to determine which Quarq power meters are compatible with 10 speed Dura-Ace 7900 chainrings.