Nerf has come up with a lot of ways to display their blasters using barrel extensions, but looks are not the only purpose for these extensions. If the barrels are used properly the can do some preformance ehancing without modifing the blaster!
Arguably the best barrel extention made by Nerf is the N-Strike Spectre REV-5 extension. This barrel does not affect blaster ranges at all but does well for mods regarding appearance.
Another extension is the popular barrel extension from the Longstrike CS-6 this part of the gun decreases range and serves little purpose other than aesthetics.
The extension that comes with the Longshot CS-6 will improve accuracy a slight amount but reduce range, plus it come with a single-shot blaster of its own!
The last extension is the Recon CS-6 barrel it adds a fairly noticeable accuracy increase but does affect range. It is also one of the better looking and most commonly used barrel extension.