They are 2117 so really a 400 spine but at 22.5” they are stiff enough. They group consistently with broad heads and field tips. I shoot 100 gr Muzzy broad heads. Going to try 125 gr next but I already had the 100’s so I went with them. Another thing to note is I shoot at 125 lbs not 150. I don’t see the need for 150 because my hunting yardage is never really over 30yds. Mini has plenty of speed at that range and with the red dot zeroed at 25yd I’m killing anything out to 30 without holding high or low (although I do adjust).