From Finjak

Made of hi-strength Acetal resin, the Finjak replaces the stock screw and sliding plate and eliminates the need for tools to install, remove, and adjust the position of the classic Bahne-style fin.

Bill Bahne introduced his Fins Unlimited box in 1971, and the Bahne-based removable/ adjustable fin system remains the standard for classic single-fin and 2+1 equipped surfboards and stand-up paddle boards.

The convenience of a fast, tool-free fin system allows easy stacking for transport (and less tear-through of board bags), but the greatest performance advantage of the tool-free Finjak is the ability to fine-tune your ride “Between sets—not Sessions!”

The Finjak works on front-tab fins, but I designed it for rear tab fins. If youre using it on a front tab fin and you hit something in the water, it could release, especially on longer fins. This can be a good thing, saving a broken fin or box, (or person). It’s a good practice to check your board whenever you hit something, but especially important when using a front-tab fin.