DESIRED FIT CAN DEPEND ON EXPERIENCE AND PERFORMANCE.
If you climb V4 or 5.12A and under: So iLL recommends those who use men's sizing to order a size and a half up. Example: If you wear a men's size 9 sneaker, select size M10.5 / W12. If you wear women's, So iLL recommends you to order your sneaker shoe size. Example: If you wear a women's size 9 sneaker, select size M9 / W10.5.
If you climb V5 or 5.12B and above: If you wear men's, So iLL recommends you to order a half size up. Example: If you wear a men's size 9 sneaker, select size M9.5 / W11. So iLL recommends those who use women sizing to order one size down. Example: If you wear a women's size 9 sneaker, select size M8 / W9.5.