These are wet socks made from hyper-thermo material by FINE EQUIPMENT. I purchased them in December 2024, but they were too big and didn't fit. The size is around 23cm. They will be too big for those with smaller feet. You might not mind them once you get used to them, but my child (who was 20cm at the time) seemed to notice. This brand has a factory in Hayama and apparently offers repairs through sales agents (I was told this about their wetsuits).