Very! I'm going to modify a weaver/Picatinny rail to fit it and use the 4x32 Centerpoint scope I have in my parts stash from the Optimus I bought my son. Seems to me they had a very odd-looking scope mount for these with a small, 4x pencil scope? Cleaned barrel bore finally. Wow, was it filthy!http://imageshack.com/a/img924/171/pdvcPT.jpg http://imageshack.com/a/img922/4265/Kj872p.jpg