Pass multiple params to the current page with form_tag in Rails

I want to pass several params in the url of the current page with a form_tag but I have failed to understand to correct syntax.



Quick explanation: I have outfits (model) that has many outfit_items (model).

Each outfit_item has available_sizes (attribute of outfit_item). All of this is set by the admin.



Then on the show page of an Outfit, (for example http://localhost:3000/outfits/7) I want to display the available sizes for each outfit_item, let the visitor pick his size for each item and press submit. The selected sizes should then appear in the URL. Here is what I have in my show view, at the url :

<%= form_tag(@outfit_path, :method=>'post') do %>
    <% @outfit.outfit_items.each do |outfit_item| %>
        <div class="col-md-2 col-sm-6 col-xs-6">
            <%= image_tag outfit_item.item_image.url(:medium) %><br>
            <% sizes = outfit_item.available_sizes.split(",") %>
            <%= select_tag "size#{outfit_item.category}", "<option>#{sizes[1]}</option><option>#{sizes[2]}</option><option>#{sizes[3]}</option><option>#{sizes[4]}</option>".html_safe, :class => "input-mini select-mini" %><br>
            <%= hidden_field_tag "size#{outfit_item.category}", value: outfit_item.category %>
        </div>
    <% end %>
            <%= submit_tag "ok size"  %>
<% end %>

I want to land on this url when I hit submit

http://localhost:3000/outfits/7?size1=42&size2=L&size3=S&size4=44

Thanks for your help