Bearing SCAR (BCAR)

Bearing SCARs (or BCAR as they are more accurately known) are the new hotness when it comes to accuracy in the nerf hobby. By inducing a spin in the dart as it leaves the barrel, the dart becomes more stable in flight and thus, goes where you want it to.
 
The principle difference over conventional SCARs is the use of bearings. Essentially little metal wheels moulded into the sides of the device, the bearings are angled which induces the spin as the dart passes. Unlike SCARs however, there is a lot less friction between the dart and the device which means a lot of the dart's energy is preserved.
 
The really work too. I've replaced the fixed SCAR on most of my high powered stuff. I'm a complete BCAR convert after seeing the difference.
 
There are two different devices available:
15° bearing angle over three rows.
8° bearing angle over 5 rows.
You will need to do some research to work out which will be most suitable for your application.
 
BCAR stands for Bearing Centred Auto Rotating according to developers in that field... just in case you were wondering.