WC Custom product meta

Woocommerce-product-meta.php

<?php

// Display Fields
add_action( 'woocommerce_product_options_general_product_data', 'woo_add_custom_general_fields' );

// Save Fields
add_action( 'woocommerce_process_product_meta', 'woo_add_custom_general_fields_save' );

function woo_add_custom_general_fields() {

	global $woocommerce, $post;

	echo '<div class="options_group">';

	// Custom fields will be created here...
	
	// Text Field
	woocommerce_wp_text_input( 
		array( 
			'id'          => 'vi_produt_count', 
			'label'       => __( 'Product count', 'woocommerce' ), 
			'placeholder' => 'Enter split count',
			'desc_tip'    => 'true',
			'description' => __( 'Enter the custom product count here.', 'woocommerce' ) 
		)  
	);
	
	echo '</div>';

}

function woo_add_custom_general_fields_save( $post_id ){
	
	// Text Field
	$woocommerce_text_field = $_POST['vi_produt_count'];
	if( !empty( $woocommerce_text_field ) )
		update_post_meta( $post_id, 'vi_produt_count', esc_attr( $woocommerce_text_field ) );

}

Found in http://www.remicorson.com/mastering-woocommerce-products-custom-fields/