diff --git a/models/products.ts b/models/products.ts
index 749bdbb..f3f6792 100644
--- a/models/products.ts
+++ b/models/products.ts
@@ -2,7 +2,7 @@ export interface Product {
   _id?: string;
   name: string;
   description: string;
-  unitType: string;
+  unitType: 'pcs' | 'gr' | 'kg' | 'ml';
   category: string;
   enabled?: boolean;
   // Stock management fields