Universal quick release skewer for placing your bike in the trainer or direct drive. This axle replaces the standard quick release, allowing racing bikes and mountain bikes to be used with Tacx trainers. Cylindrical shaped ends and flat outer surfaces make it easy to mount your rear wheel into your Tacx trainer*. FEATURES : Don't damage your bikes stock QR when mounting it on a trainer Great as a replacement for a lost skewer Ideal if you want to use more than one bike with your trainer. 5mm axle diameter. * This QR skewer will work with most makes of indoor trainer