The smallest chainring that typically fits on a Quarq SRAM XX1 Eagle DUB Power Meter is a 32T round chainring or a 34T oval. This is because if the chainring is smaller than this, it can interfere (make contact) with the power meter spider. However, in some cases, you can mount a 30T round or 32T oval chainring on a Quarq. Specifically, if the chainring in question has an offset built into the chainring holes, it should work.
For example, many 30T round and 32T oval chainrings have extra chainring material (see image below) around the bolt holes. This works to create a small space (usually about 1 mm) between the power meter and the chainring, therefore allowing the chainring to attach properly on the power meter. Please note, this chainring offset means your chainline will move 1 mm inboard. This shouldn’t have a noticeable impact on the operation of your drivetrain but it’s worth making note of.
If you have questions on a specific chainring that we carry, we are happy to test it on the power meter to confirm compatibility for you!