Hello, Below are the answers to your questions. Size Accuracy: If you typically wear a size 41, a size 41.5 will be approximately 0.5 cm longer. If size 41 fits your foot perfectly, size 41.5 may be a little big. However, if size 41 feels tight, size 41.5 would be a more comfortable choice. Buying half a size larger in these types of shoes usually provides extra comfort. Wet Surface Use Cloudfoam-based shoes are designed to provide lightness and cushioning and are daily use shoes. This sole structure may have poor grip performance on wet and slippery surfaces. Therefore, we recommend exercising caution on rainy or wet surfaces.