Hide select size box on select products

Site URL: https://www.matitaconcept.com/

Hi, 

How can I hide the box of: select size?

I have already hidden the quantity box:

#block-f54834bf7393be8d6fe9  .product-quantity-input {
display:none !important;
}

#block-3fc9187dbc4909c9d1fa .product-quantity-input {
display:none !important;
}

#block-b30d509c83712d92ecfe .product-quantity-input {
display:none !important;
}

thank you,

elena

Hi. What is password?