M Means The Standard Width Sole material:Rubber Please allow 1-3mm error due to manual measurement. Due to light or display setting please understand that there may be color difference. Shoe upper material: Knit Fashion :Character Style:Casual Description Gender:Girls/Boys Insole Length=Foot Length+0.8cm It is made of high quality materials Soft hand feeling your baby Package content:1 pair baby sock shoes(Not Including shoes box) If you are not sure which size or other problems please contact us to make sure you choose correct size. and design available Make your baby more Size chart: Size:18/19 Recommended Age:3-6 Months EU:20 UK:3.5 US:4.5M Insole Length:11.5cm/4.53 Size:20/21 Recommended Age:9-12 Months EU:21 UK:4.5 US:5.5M Insole Length:12.5cm/4.92 Size:22/23 Recommended Age:15-18 Months EU:22.5 UK:5.5 US:6.5M Insole Length:13.5cm/5.31 Size:24/25 Recommended Age:2-2.5 Years EU:24 UK:7 US:8M Insole Length:14.5cm/5.71 Size:26/27 Recommended Age:3-3.5 Years EU:26 UK:9 US:9M Insole Length:15.5cm/6.10