Our Red Paddle Co flexi fin is supplied with a nut and bolt connection to ensure a 100% secure hold and is compatible with all US fin boxes.
Here is our video, which you can find in the Red Paddle Co Clubhouse on how to fit a fin using a 'Quick-fit US Fin Bolt':
https://redpaddleco.com/clubhouse/maintenance-tips/how-to-fit-your-red-paddle-co-fin/
Fin height = 9" from the bottom of the board. Base length = 6.5"