This is a Barrel extension I designed for my NERF Stryfe, it has a clean outside and a decorative barrel rifling on the inside. Should fit other NERFs that support bayonet barrel extensions.

Designed in OnShape: https://cad.onshape.com/documents/fa3e34bb465a253d7817d529/w/8e7108d1335bbf100e561f57/e/f89d5c7e0345e26ca3927680