Buffer 120/150: This is a double side Buffer. The 120 side has a coarse grit and is used to remove any roughness or ridges on the surface of the nail extension. It can also be used to shape and shorten nails. The 150 side has a slightly finer grit and is used to smooth out the nail surface and prepare it for polishing or further shaping. It can also be used to buff out any scratches left by the 120 grit buffer.