The Thule 15mm thru-axle adapter is exactly what you'll need to attach your 15mm thru-axle fork to roof mount your mountain bike on a fork mounted bike carrier
If you're riding a Cannondale Lefty fork, then you'll want to put one of these adapters in your bike kit when you need to carry your bike on a fork-mounted, roof bike rack
The Thule Xadapt 9 enables you to attach your Thule 517 Peloton, Thule 518 Echelon, or Thule 594 SideArm bike rack to your Thule Aluminum Aero Crossbar
The Thule Xadapt 2 enables you to attach your Thule 599XTR Ultimate Upright Bike Rack or your Thule 724 & 725 Flat Top Ski Rack to your Thule Aero Crossbar
The Road Shower is a great pressurized, solar heated water supply for your vehicle's roof rack system which is perfect for outdoor showers, camping, and other recreational sports