The park tool tns 1 threadless nut setter is used to install star fangled nuts found on threadless headset systems thread the nut onto the tns 1 insert into the fork stack and tap it in with a hammer sets the starfangled nut to 15mm and keeps it straight long handle helps prevent pinched fingers park tool tns 1 threadless nut setter features eliminate the guesswork out of fitting the star nut fits 1 inch and 1 18 inch steerer tubes sets the star nut to 15 m