This clamp is designed to fix the wing on the fork. In my case, the BOLANY Bike Fork Rebound Adjustable MTB Air Front Suspension 29 Inch 120mm fork is used. 

The inner diameter of the clamp is 38 mm. This is enough to fix it on forks with a diameter of 39 mm.

PLA is enough for printing. It is advisable to use a border. Without support 

For fixing to the wing, the complete M5 hardware is used.