diff --git a/src/Entity/ModelType.php b/src/Entity/ModelType.php
index c42458f..7f68799 100644
--- a/src/Entity/ModelType.php
+++ b/src/Entity/ModelType.php
@@ -221,7 +221,7 @@ class ModelType
         return match ($this->category) {
             ModelCategory::COMPONENT => $this->getComponentStructureFromRelations(),
             ModelCategory::PIECE     => $this->getPieceStructureFromRelations(),
-            ModelCategory::PRODUCT   => ['customFields' => []],
+            ModelCategory::PRODUCT   => ['customFields' => $this->serializeCustomFields($this->productCustomFields)],
         };
     }
 
@@ -344,7 +344,7 @@ class ModelType
 
     private function getComponentStructureFromRelations(): array
     {
-        $structure = ['customFields' => [], 'pieces' => [], 'products' => [], 'subcomponents' => []];
+        $structure = ['customFields' => $this->serializeCustomFields($this->customFields), 'pieces' => [], 'products' => [], 'subcomponents' => []];
 
         foreach ($this->skeletonPieceRequirements as $req) {
             $structure['pieces'][] = [
@@ -373,11 +373,34 @@ class ModelType
     private function getPieceStructureFromRelations(): array
     {
         return [
-            'customFields' => [],
+            'customFields' => $this->serializeCustomFields($this->pieceCustomFields),
             'products'     => array_map(fn (SkeletonProductRequirement $req) => [
                 'typeProductId' => $req->getTypeProduct()->getId(),
                 'familyCode'    => $req->getFamilyCode(),
             ], $this->skeletonProductRequirements->toArray()),
         ];
     }
+
+    /**
+     * @param Collection<int, CustomField> $fields
+     */
+    private function serializeCustomFields(Collection $fields): array
+    {
+        $items = [];
+        foreach ($fields as $cf) {
+            $items[] = [
+                'id'           => $cf->getId(),
+                'name'         => $cf->getName(),
+                'type'         => $cf->getType(),
+                'required'     => $cf->isRequired(),
+                'options'      => $cf->getOptions(),
+                'defaultValue' => $cf->getDefaultValue(),
+                'orderIndex'   => $cf->getOrderIndex(),
+            ];
+        }
+
+        usort($items, static fn (array $a, array $b) => $a['orderIndex'] <=> $b['orderIndex']);
+
+        return $items;
+    }
 }