diff --git a/web/typo3conf/ext/ep_products/Classes/Domain/Model/FilterSettings.php b/web/typo3conf/ext/ep_products/Classes/Domain/Model/FilterSettings.php
index 2a96981c..641dfb03 100644
--- a/web/typo3conf/ext/ep_products/Classes/Domain/Model/FilterSettings.php
+++ b/web/typo3conf/ext/ep_products/Classes/Domain/Model/FilterSettings.php
@@ -2,6 +2,8 @@
 
 namespace EP\EpProducts\Domain\Model;
 
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+
 /***************************************************************
  *
  *  Copyright notice
@@ -199,7 +201,8 @@ class FilterSettings implements \JsonSerializable
             $filterSettings->setRegionUids([$searchParams['region']]);
         }
         if (!empty($searchParams['concept'])) {
-            $filterSettings->setConceptUids([$searchParams['concept']]);
+            $conceptUids = GeneralUtility::trimExplode(',', $searchParams['concept']);
+            $filterSettings->setConceptUids($conceptUids);
         }
         if (!empty($searchParams['hotel'])) {
             $filterSettings->setHotelUid($searchParams['hotel']);
diff --git a/web/typo3conf/ext/ep_products/Configuration/TCA/tx_epproducts_domain_model_staticsearchparams.php b/web/typo3conf/ext/ep_products/Configuration/TCA/tx_epproducts_domain_model_staticsearchparams.php
index 1204cf0f..03c180a2 100644
--- a/web/typo3conf/ext/ep_products/Configuration/TCA/tx_epproducts_domain_model_staticsearchparams.php
+++ b/web/typo3conf/ext/ep_products/Configuration/TCA/tx_epproducts_domain_model_staticsearchparams.php
@@ -149,11 +149,12 @@ return [
             'label' => 'Konzept',
             'config' => [
                 'type' => 'select',
-                'renderType' => 'selectSingle',
+                'renderType' => 'selectSingleBox',
                 'foreign_table' => 'tx_epproducts_domain_model_concept',
                 'foreign_table_where' => 'AND 1=1 ORDER BY name',
                 'minItems' => 0,
-                'maxitems' => 1,
+                'maxitems' => 10,
+                'size' => 5,
                 'items' => [
                     [ 'Keine Auswahl', 0 ],
                 ]
diff --git a/web/typo3conf/ext/ep_products/ext_tables.sql b/web/typo3conf/ext/ep_products/ext_tables.sql
index f71f06df..4d2e46a2 100644
--- a/web/typo3conf/ext/ep_products/ext_tables.sql
+++ b/web/typo3conf/ext/ep_products/ext_tables.sql
@@ -1034,7 +1034,7 @@ CREATE TABLE tx_epproducts_domain_model_staticsearchparams (
 	date_to date DEFAULT '0000-00-00',
 	bus tinyint(1) unsigned DEFAULT '0' NOT NULL,
 	product int(11) unsigned DEFAULT '0',
-	concept int(11) unsigned DEFAULT '0',
+	concept varchar(255) DEFAULT '' NOT NULL,
 	country int(11) unsigned DEFAULT '0',
 	region int(11) unsigned DEFAULT '0',
 	hotel int(11) unsigned DEFAULT '0',