diff --git a/xair_api/kinds.py b/xair_api/kinds.py
index dc00991..2bb693d 100644
--- a/xair_api/kinds.py
+++ b/xair_api/kinds.py
@@ -1,15 +1,16 @@
 from dataclasses import dataclass
 
 
-@dataclass
+@dataclass(frozen=True)
 class KindMap:
+    id_: str
+
     def __str__(self) -> str:
         return self.id_
 
 
-@dataclass
+@dataclass(frozen=True)
 class X32KindMap(KindMap):
-    id_: str
     num_dca: int = 8
     num_strip: int = 32
     num_bus: int = 16
@@ -19,28 +20,25 @@ class X32KindMap(KindMap):
     num_headamp: int = 127
 
 
-@dataclass
+@dataclass(frozen=True)
 class XR18KindMap(KindMap):
     # note ch 17-18 defined as aux return
-    id_: str
     num_dca: int = 4
     num_strip: int = 16
     num_bus: int = 6
     num_fx: int = 4
 
 
-@dataclass
+@dataclass(frozen=True)
 class XR16KindMap(KindMap):
-    id_: str
     num_dca: int = 4
     num_strip: int = 16
     num_bus: int = 4
     num_fx: int = 4
 
 
-@dataclass
+@dataclass(frozen=True)
 class XR12KindMap(KindMap):
-    id_: str
     num_dca: int = 4
     num_strip: int = 12
     num_bus: int = 2
@@ -60,4 +58,4 @@ def get(kind_id):
     return _kinds[kind_id]
 
 
-all = list(kind for kind in _kinds.values())
+all = list(_kinds.values())