Multiple selection in select box in Rhtml

select_tag('letters', options_for_select(['A','B','C','D'], 'A'), :size => 5, :multiple => true)

You need to add the to the name to get back an array of selected values.

That works great! Thanks!! But what if I need to display the form with more then one value already selected? I tried

  select_tag('letters', options_for_select(['A','B','C','D'],'A','B'), :size =>5, :multiple => true)

but that raised the following error: "Wrong number of arguments (3 for 2)".

Any suggestions?