A banana hand file in 100/180 grit. The banana curve is the shape for working the sidewalls and the underside of the free edge, where a straight file cannot sit flat against the nail.
Reading the grit numbers
Two numbers means two sides. The lower number is the coarser face, for shaping and taking length down; the higher one refines the edge afterwards. 80/100 is aggressive, for tips and hard gel; 100/180 is the everyday working pair; 180/240 is finishing only.
