Depends on how fast you want to go, how efficient your setup should be and also on your skills and riders weight. Wings from 800 to 1600 or even bigger work for efoils.
Gong Allvator M or L , pro MT, Veloce all work.
RL also has 2 wings designed specifically for efoils, one is 1150cm2, the bigger one is 1600cm2. Both work well, with the smaller one you can go up to 40km/h, a bit slower with the bigger one. See here: New RL efoil wing - #39 by kiterr
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