What crankset do you have now?

how many bolts?

find the one that matches here, with desired BCD (110 for compact gearing (50/34 or 52/36) or 130 for standard 53/39 and up)
https://www.quarq.com/product-category/power-meters/shimano/#sm.00001y5beua1h1fkcrnf84w4838rm

For the Trek BB90 bottom bracket you will need a GXP Quarq. If you have a Shimano crankset on the bike now, you will need a new BB bearing kit for GXP from Trek. It will have a smaller NDS 22mm bearing and the proper shields and seals for the GXP.

The you just have to decide on which Quarq spider/chainring system and crank length you want. Basically you can go with the 4 bolt Shimano chainrings or industry standard 5 bolt chainrings. With either choice you have two additional choices - Shimano 9000 series or latest 9100 series rings - or standard 5 bolt vs SRAM hidden bolt rings.

Choosing between carbon and aluminum arms means a slight weight difference and a bit shorter arm length choice with carbon.

Hope this helps

I have dura ace 9000 55/42

Quarq DFour is the match for that cranskset if you want to continue using 9000 series rings. Or DFour91 if you want to use the 9100 series rings.

This one then: https://www.quarq.com/...ua1h1fkcrnf84w4838rm

You need a GXP quarq (not bb30) and then you need a new bb in your SC (GXP bearings from trek).

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