they are the weirdest shape ive seen for a speed fin.

any pictures of slingshot ?

Used 23cm Slingshot today, Board was Nude Streaker 54, and sail TR-6 6.6m. Have to say I was impressed with the slingshot, for such a small fin it hinks up wind, handles chop, and definitely fast, impressed.

used the 21 in very choppy 30+ n/east today, the fin let go a couple of time when using a 5.0 koncept in about 20 to 25 knts, rigged the rs4.6 when the wind kicked in too 30+ i was surprised how well the fin held up after some very ordinary landings, at times it felt there was to much fin but it could have been the drive in the sail,
i would have liked to try the 19 but may have been a bit short for the heavy chop,the combo was a perfect, some gusts would have been 35 and at no time did i feel out of control, the sail felt rock solid and as light as
for the whole session I'm thinking how much wind does this gear need