mikeyarce/gallery-thumbnail.php

## gallery-thumbnail.php
<?php
add_filter( 'woocommerce_get_image_size_gallery_thumbnail', function( $size ) {
	return array(
		'width'  => 400,
		'height' => 400,
		'crop'   => 1,
	);
} );
	<?php
	add_filter( 'woocommerce_get_image_size_gallery_thumbnail', function( $size ) {
	return array(
	'width' => 400,
	'height' => 400,
	'crop' => 1,
	);
	} );