I have an MP5 Swordfish AEG and it originally came with a 6.05mm ID, 110mm length brass inner barrel. It shot groupings of 18" wide at 120'. With my new barrel 6.01 ID, 140mm length it now shoots groupings of 5" wide at 120' a vast improvement! In fact it can reliably hit a human sized target at almost 200' reliably! I highly recommend buying one of these inner barrels they are the "BANG!" for the buck! I would give this item 10 stars if I could.