Are hollow women's shoes sandals or single shoes

Hollow women's shoes are a popular kind of shoes, which can be sandals or single shoes. Sandals are mainly worn in summer, and the soles are made of cool materials such as mesh and weaving to keep the air circulation of the soles comfortable and cool; Single shoes are mostly worn in winter, and the sole material is thick, which is warm and comfortable. Usually, hollow design is adopted, which is more fashionable.