Electronic commerce: what is the best way to select the size of the clothes?

The radio buttons are (usually) more convenient to use than the drop-down menus.

The advantage of the option buttons is twofold: they allow the user to see all the options at once and only require a user click.

The drop-down menus not only hide your options, but require at least two clicks to use them (that is, one to show the options and one to select an option). Sometimes the user has to click on a scroll bar and drag it.

It is true that most of the drop-down menus allow you to jump to the options by "typing focus", but doing so is more effort than selecting from a set of option buttons. Drop-down menus are only useful when their sets of options are predictable to the user, such as EE states. UU

The best design is a vertical, smaller list of standard radio buttons. I would recommend not using an unconventional style because there is a possibility that a user does not recognize their radio buttons.