This is a hybrid compensator and muzzle break, but will still help to diminish the flash.
The flash you experience can be GREATLY adjusted by altering your barrel length and ammunition. As a rule of thumb, a shorter barrel such as a 10.5" will have much more flash than a standard 16" barrel (which is the length we recommend running the NERO 556 on). As for ammunition, it depends on how hot the ammo is as well as the flash retardant in the powder formula. Different brands have differing amounts (and this could vary greatly). We do not market the NERO 556 as a flash hider but you can take steps to reduce any flash you may experience. Using a higher-end .223 Remington duty load designed for LE for example (something like Hornady TAP) can greatly reduce any flash experienced if any on a 16" patrol carbine.
If you're looking strictly for a flash hider I would look elsewhere. Especially if you're running on an SBR or 5.56 "pistol". I have this on a 7.5in barrel and the fireballs are insane.