The Quarq SRAM XX1 Eagle DUB Power Meter works with SRAM XX1 Eagle DUB 8-bolt cranksets. So assuming you currently have a SRAM crankset, you need to look on the backside of your chainring and confirm you have the 8-bolt pattern. If you do, you are good to go and can just but the power meter spider for $599 and bolt it onto your existing crankset.
If you have the 3-bolt pattern instead, this means your SRAM crankset is not compatible with the XX1 Power Meter, in which case you have two options.
Option 1 – Buy the SRAM XX1 Eagle DUB 8-bolt crankset, which can be bundled with the power meter right on our product page. This way, you will now have a compatible crankset for the power meter spider. Please note, you will also need a SRAM DUB bottom bracket as well.
Option 2 – Buy the power2max SRAM MTB Power Meter instead. The power2max is a very similar spider-based MTB power meter but it fits with 3-bolt SRAM cranksets, so there is no need to change your crankset.
Please note, both of these power meters use a 104 BCD chainring configuration and require appropriate MTB chainrings.