diff --git a/htdocs/variants/class/ProductAttribute.class.php b/htdocs/variants/class/ProductAttribute.class.php
index 52ee3153108..bbc3a188137 100644
--- a/htdocs/variants/class/ProductAttribute.class.php
+++ b/htdocs/variants/class/ProductAttribute.class.php
@@ -41,6 +41,12 @@ class ProductAttribute extends CommonObject
 	 */
 	public $ref;
 
+	/**
+	 * External ref of the product attribute
+	 * @var string
+	 */
+	public $ref_ext;
+
 	/**
 	 * Label of the product attribute
 	 * @var string
@@ -79,7 +85,7 @@ class ProductAttribute extends CommonObject
 			return -1;
 		}
 
-		$sql = "SELECT rowid, ref, label, rang FROM ".MAIN_DB_PREFIX."product_attribute WHERE rowid = ".(int) $id." AND entity IN (".getEntity('product').")";
+		$sql = "SELECT rowid, ref, ref_ext, label, rang FROM ".MAIN_DB_PREFIX."product_attribute WHERE rowid = ".(int) $id." AND entity IN (".getEntity('product').")";
 
 		$query = $this->db->query($sql);
 
@@ -91,6 +97,7 @@ class ProductAttribute extends CommonObject
 
 		$this->id = $obj->rowid;
 		$this->ref = $obj->ref;
+		$this->ref_ext = $obj->ref_ext;
 		$this->label = $obj->label;
 		$this->rang = $obj->rang;
 
@@ -106,7 +113,7 @@ class ProductAttribute extends CommonObject
 	{
 		$return = array();
 
-		$sql = 'SELECT rowid, ref, label, rang FROM '.MAIN_DB_PREFIX."product_attribute WHERE entity IN (".getEntity('product').')';
+		$sql = 'SELECT rowid, ref, ref_ext, label, rang FROM '.MAIN_DB_PREFIX."product_attribute WHERE entity IN (".getEntity('product').')';
 		$sql .= $this->db->order('rang', 'asc');
 		$query = $this->db->query($sql);
 		if ($query)
@@ -115,6 +122,7 @@ class ProductAttribute extends CommonObject
 				$tmp = new ProductAttribute($this->db);
 				$tmp->id = $result->rowid;
 				$tmp->ref = $result->ref;
+				$tmp->ref_ext = $result->ref_ext;
 				$tmp->label = $result->label;
 				$tmp->rang = $result->rang;
 
@@ -147,8 +155,8 @@ class ProductAttribute extends CommonObject
 		//Ref must be uppercase
 		$this->ref = strtoupper($this->ref);
 
-		$sql = "INSERT INTO ".MAIN_DB_PREFIX."product_attribute (ref, label, entity, rang)
-		VALUES ('".$this->db->escape($this->ref)."', '".$this->db->escape($this->label)."', ".(int) $this->entity.", ".(int) $this->rang.")";
+		$sql = "INSERT INTO ".MAIN_DB_PREFIX."product_attribute (ref, ref_ext, label, entity, rang)
+		VALUES ('".$this->db->escape($this->ref)."', '".$this->db->escape($this->ref_ext)."', '".$this->db->escape($this->label)."', ".(int) $this->entity.", ".(int) $this->rang.")";
 
 		$query = $this->db->query($sql);
 		if ($query)
@@ -183,7 +191,7 @@ class ProductAttribute extends CommonObject
 		$this->ref = trim(strtoupper($this->ref));
 		$this->label = trim($this->label);
 
-		$sql = "UPDATE ".MAIN_DB_PREFIX."product_attribute SET ref = '".$this->db->escape($this->ref)."', label = '".$this->db->escape($this->label)."', rang = ".(int) $this->rang." WHERE rowid = ".(int) $this->id;
+		$sql = "UPDATE ".MAIN_DB_PREFIX."product_attribute SET ref = '".$this->db->escape($this->ref)."', ref_ext = '".$this->db->escape($this->ref_ext)."', label = '".$this->db->escape($this->label)."', rang = ".(int) $this->rang." WHERE rowid = ".(int) $this->id;
 
 		if ($this->db->query($sql)) {
 			return 1;
diff --git a/htdocs/variants/class/ProductCombination.class.php b/htdocs/variants/class/ProductCombination.class.php
index b05696ca534..72d7ba7c1a8 100644
--- a/htdocs/variants/class/ProductCombination.class.php
+++ b/htdocs/variants/class/ProductCombination.class.php
@@ -77,6 +77,12 @@ class ProductCombination
 	 */
 	public $combination_price_levels;
 
+	/**
+     * External ref
+     * @var string
+     */
+    public $variation_ref_ext = '';
+
 	/**
 	 * Constructor
 	 *
@@ -100,7 +106,7 @@ class ProductCombination
 	{
 		global $conf;
 
-		$sql = "SELECT rowid, fk_product_parent, fk_product_child, variation_price, variation_price_percentage, variation_weight FROM ".MAIN_DB_PREFIX."product_attribute_combination WHERE rowid = ".(int) $rowid." AND entity IN (".getEntity('product').")";
+		$sql = "SELECT rowid, fk_product_parent, fk_product_child, variation_price, variation_price_percentage, variation_weight, variation_ref_ext FROM ".MAIN_DB_PREFIX."product_attribute_combination WHERE rowid = ".(int) $rowid." AND entity IN (".getEntity('product').")";
 
 		$query = $this->db->query($sql);
 
@@ -120,6 +126,7 @@ class ProductCombination
 		$this->variation_price = $obj->variation_price;
 		$this->variation_price_percentage = $obj->variation_price_percentage;
 		$this->variation_weight = $obj->variation_weight;
+        $this->variation_ref_ext = $obj->variation_ref_ext;
 
 		if (!empty($conf->global->PRODUIT_MULTIPRICES)) {
 			$this->fetchCombinationPriceLevels();
@@ -226,7 +233,6 @@ class ProductCombination
 		}
 	}
 
-
 	/**
 	 * Retrieves information of a variant product and ID of its parent product.
 	 *
@@ -295,6 +301,7 @@ class ProductCombination
 			$tmp->variation_price = $result->variation_price;
 			$tmp->variation_price_percentage = $result->variation_price_percentage;
 			$tmp->variation_weight = $result->variation_weight;
+            $tmp->variation_ref_ext = $result->variation_ref_ext;
 
 			if (!empty($conf->global->PRODUIT_MULTIPRICES)) {
 				$tmp->fetchCombinationPriceLevels();
@@ -339,10 +346,10 @@ class ProductCombination
 		/* $this->fk_product_child may be empty and will be filled later after subproduct has been created */
 
 		$sql = "INSERT INTO ".MAIN_DB_PREFIX."product_attribute_combination";
-		$sql .= " (fk_product_parent, fk_product_child, variation_price, variation_price_percentage, variation_weight, entity)";
+		$sql .= " (fk_product_parent, fk_product_child, variation_price, variation_price_percentage, variation_weight, variation_ref_ext, entity)";
 		$sql .= " VALUES (".((int) $this->fk_product_parent).", ".((int) $this->fk_product_child).",";
 		$sql .= (float) $this->variation_price.", ".(int) $this->variation_price_percentage.",";
-		$sql .= (float) $this->variation_weight.", ".(int) $this->entity.")";
+		$sql .= (float) $this->variation_weight.", '".$this->db->escape($this->variation_ref_ext)."', ".(int) $this->entity.")";
 
 		$resql = $this->db->query($sql);
 		if ($resql) {
@@ -375,7 +382,8 @@ class ProductCombination
 		$sql = "UPDATE ".MAIN_DB_PREFIX."product_attribute_combination";
 		$sql .= " SET fk_product_parent = ".(int) $this->fk_product_parent.", fk_product_child = ".(int) $this->fk_product_child.",";
 		$sql .= " variation_price = ".(float) $this->variation_price.", variation_price_percentage = ".(int) $this->variation_price_percentage.",";
-		$sql .= " variation_weight = ".(float) $this->variation_weight." WHERE rowid = ".((int) $this->id);
+		$sql .= " variation_ref_ext = '".$this->db->escape($this->variation_ref_ext)."',";
+        $sql .= " variation_weight = ".(float) $this->variation_weight." WHERE rowid = ".((int) $this->id);
 
 		$resql = $this->db->query($sql);
 		if (!$resql) {
@@ -663,9 +671,10 @@ class ProductCombination
 	 * @param bool|float 	$forced_pricevar 	If the price variation is forced
 	 * @param bool|float 	$forced_weightvar 	If the weight variation is forced
 	 * @param bool|string 	$forced_refvar 		If the reference is forced
+     * @param string 	    $ref_ext            External reference
 	 * @return int 								<0 KO, >0 OK
 	 */
-	public function createProductCombination(User $user, Product $product, array $combinations, array $variations, $price_var_percent = false, $forced_pricevar = false, $forced_weightvar = false, $forced_refvar = false)
+	public function createProductCombination(User $user, Product $product, array $combinations, array $variations, $price_var_percent = false, $forced_pricevar = false, $forced_weightvar = false, $forced_refvar = false, $ref_ext = '')
 	{
 		global $db, $conf;
 
@@ -781,6 +790,7 @@ class ProductCombination
 		$newcomb->variation_price_percentage = $price_var_percent;
 		$newcomb->variation_price = $price_impact[1];
 		$newcomb->variation_weight = $weight_impact;
+        $newcomb->variation_ref_ext = $db->escape($ref_ext);
 
 		// Init price level
 		if ($conf->global->PRODUIT_MULTIPRICES) {