Exactly what I needed for my Seekins Havak HIT. Took some internet sleuthing to find out if this would work and still wasn’t 100% positive it would. I can definitively tell you, it fits and allows you to swap out the plethora of available bolt knobs on the market. The rifle-end threading was extremely tight in the female bolt threads. It was so tight that I had to attach the knob and use vice grips to crank it all the way down. No concerns that it will come off. Length is adequate although options for length and angle would be appreciated. I have this adapter on both of my Havak HITs.