How to add item attribute to cart?

Question

WordPress

I put the goods in the cart with Ajax, everything adds but does not add the attribute (size) I will
add using this
$WC_Cart = new WC_Cart();
$WC_Cart->add_to_cart( $product_id, $quantity, $variation_id, $variation, $cart_item_data );
can you show an example how to pass attribute and value there? and then I'm a little dumb, I did not find examples (