SIZING INFORMATION The type of desired fit can depend on experience and performance. If you climb V4 or 5.12A and under: So iLL recommends those who use women sizing to order their street shoe size. Example: If you wear a women's size 9 street shoe, order the women's size 9. If you wear men's, So iLL recommends you to order a size and a half up. Example: If you wear a men's size 9 street shoe, order size 10.5 here. If you climb V5 or 5.12B and above: So iLL recommends those who use women sizing to order one size down. Example: If you wear a women's size 9 street shoe, order the women's size 8. If you wear men's, So iLL recommends you to order a half size up. Example: If you wear a men's size 9 street shoe, order size 9.5 here. NOTE: The New Zero is considered men's sizing. Though they can be worn by men or women, sizing between styles vary and we recommend checking the sizing description before purchasing. The synthetic vegan upper fits like a slipper, and the fabric is normally used on the inside of durable work boots in the footwear industry. For a shoe at this level, it is incredibly comfortable. The thread we use for the upper is specially made in the southeast as one of the softest threads in the world, and cannot be felt in the toe box. This shoe is sensitive and every detail matters when performing at a high level. Dark Matter toe rubber meets the rand by butting up together, with no overlapping. This is incredibly hard to do in production and provides no hot spots. The New Zero is coated in "Dark Matter" rubber, part of the "UnParallel Rubber" family, a sticky outsole rubber originally formulated for the United States Navy Seals to ensure security in foot placement during approaches. It's the stickiest rubber you will experience.