Karoo fits in any bracket with a Garmin Quarter-Turn interface. At present, we are shipping Karoo with a T3 out-front Handlebar Mount. This was made specifically for the Karoo and is very sturdy. It also comes with 2 rubber shims for different size handlebars.
If you have a special handlebar and cannot use this mount, you can look here for alternate options: Compatible Aero/Non-standard handlebar mounts