The choice of skewer type to use with our BKOOL Pro2 or Bkool Go trainer depends mainly on the thickness and length of the axle that is installed on the rear wheel of your bike.
The 9-mm quick release was the most common until 12-mm thru-axles appeared on the market. If your rear wheel has a 9-mm quick release installed, you must use the release that comes with the trainer.
If, however, your rear wheel uses a 12-mm thru-axle, you must purchase one 12-mm releases.
You can easily get the Thru Axles of 12mm at our old supplier's online store: https://robertaxleproject.com/
There is a finder tool to know which axle reference you need based on your bike model.