Surf SUP fin US-box compatible, NO FinKey needed for mounting - just slide in! 130mm and 175mm height

I originally designed the first version of the small 130mm fin for river SUP'ing on the Isar south of Munich. During construction I discovered that those fins can be easily constructed without the rectangular washer, screw and possible FinKey tool needed for mounting. Just by printing the rectangular washer in the correct position and size - then just slide in the fin and print it as thick or thick it up with tape to fit exactly in your fin-box.
This release is now already the 3rd version and t