Eyelashes are not just for aesthetics. They can also protect your eyes from dust and foreign particles. If you have curly lashes, then you should use mascara that has a curved brush. Curved brushes will help your lashes curve upwards, giving them a natural curl. If you have straight lashes, then use mascara with a straight brush. Straight brushes will help your lashes curve downwards and give them the desired effect of length and fullness. So what type of lash extension you should use depends on your preference.