It comes packaged with the SharpFire and cannot be purchased separately.
Unlike other Nerf barrel extensions, the SharpFire barrel extension is only compatible with its patron blaster.
It is a short barrel that has an integrated iron sight on front end. A strap point is also built into it, located under the barrel itself. It snaps into place when loaded onto the SharpFire and removing it is as simple as pulling it straight off.
The barrel extension reportedly doesn't decrease firing ranges for the SharpFire.