The Hubboards 2mm Neoprene Fin Sock with Sock Lock. Our revolutionary fin sock uses super comfortable 2mm neoprene and is cut and flat lock stitched into a foot shaped sock that fits your foot perfectly. Our New Sock Lock technology is a built in fin tether on your fin sock. Giving you a fin tether and fin sock all in one. The sock lock works by buckling the tether on the outside of your fin strap, this allows the fin to be locked to you foot so that you do not have to worry about losing your swim fin or your fin sock ever again.