Yakima tracks - what size T-nut?

The reason for the Yakima is it fits with an optional mounting kit to mount to the Retrax Pro XR T-Slot retractable tonneau cover for mounting

Extremely quiet, aerodynamic crossbars attach to Yakima towers to create a stylish roof rack for your vehicle Rubber strips in T-slots push down to load

yakima smartslot kit 1 T-slot attachments make adding gear mounts and accessories fast and simple; Integrated SKS locks to secure your rack system to the truck bed

yakima t slot bolts This hardware kit replaces the standard mounting hardware to enable direct attachment of your bike mount into a T-slot channel on your crossbar,