diff --git a/compose_viz/models/device.py b/compose_viz/models/device.py
new file mode 100644
index 0000000..e777a3d
--- /dev/null
+++ b/compose_viz/models/device.py
@@ -0,0 +1,18 @@
+
+class Device:
+    def __init__(self, host_path: str, container_path: str, cgroup_permissions: str = None):
+        self._host_path = host_path
+        self._container_path = container_path
+        self._cgroup_permissions = cgroup_permissions
+
+    @property
+    def host_path(self):
+        return self._host_path
+
+    @property
+    def container_path(self):
+        return self._container_path
+    
+    @property
+    def cgroup_permissions(self):
+        return self._cgroup_permissions
\ No newline at end of file
diff --git a/compose_viz/models/service.py b/compose_viz/models/service.py
index 4ba1bbe..eed285c 100644
--- a/compose_viz/models/service.py
+++ b/compose_viz/models/service.py
@@ -19,7 +19,7 @@ class Service:
         extends: Optional[Extends] = None,
         cgroup_parent: Optional[str] = None,
         container_name: Optional[str] = None,
-        devices: Optional[Device] = None,
+        devices: Optional[Device] = [],
         env_file: List[str] = [],
         expose: List[str] = [],
         profiles: List[str] = [],