diff --git a/src/numpy-stubs/exceptions.pyi b/src/numpy-stubs/exceptions.pyi
index 2748a153..6f04ea78 100644
--- a/src/numpy-stubs/exceptions.pyi
+++ b/src/numpy-stubs/exceptions.pyi
@@ -17,6 +17,8 @@ class TooHardError(RuntimeError): ...
 class DTypePromotionError(TypeError): ...
 
 class AxisError(ValueError, IndexError):
+    __slots__ = "_msg", "axis", "ndim"
+
     axis: int | None
     ndim: int | None
     @overload
diff --git a/src/numpy-stubs/lib/_index_tricks_impl.pyi b/src/numpy-stubs/lib/_index_tricks_impl.pyi
index dface2d3..aac54d33 100644
--- a/src/numpy-stubs/lib/_index_tricks_impl.pyi
+++ b/src/numpy-stubs/lib/_index_tricks_impl.pyi
@@ -98,6 +98,8 @@ class ndindex:
     def ndincr(self, /) -> None: ...
 
 class nd_grid(Generic[_BoolT_co]):
+    __slots__: ClassVar[tuple[str, ...]] = ("sparse",)
+
     sparse: _BoolT_co
     def __init__(self, sparse: _BoolT_co = ...) -> None: ...
     @overload
@@ -107,14 +109,18 @@ class nd_grid(Generic[_BoolT_co]):
 
 @final
 class MGridClass(nd_grid[L[False]]):
+    __slots__ = ()
+
     def __init__(self) -> None: ...
 
 @final
 class OGridClass(nd_grid[L[True]]):
+    __slots__ = ()
+
     def __init__(self) -> None: ...
 
 class AxisConcatenator(Generic[_AxisT_co, _MatrixT_co, _NDMinT_co, _Trans1DT_co]):
-    __slots__ = "axis", "matrix", "ndmin", "trans1d"
+    __slots__: ClassVar[tuple[str, ...]] = "axis", "matrix", "ndmin", "trans1d"
 
     makemat: ClassVar[type[_nt.Matrix]]
 
@@ -147,13 +153,19 @@ class AxisConcatenator(Generic[_AxisT_co, _MatrixT_co, _NDMinT_co, _Trans1DT_co]
 
 @final
 class RClass(AxisConcatenator[L[0], L[False], L[1], L[-1]]):
+    __slots__ = ()
+
     def __init__(self, /) -> None: ...
 
 @final
 class CClass(AxisConcatenator[L[-1], L[False], L[2], L[0]]):
+    __slots__ = ()
+
     def __init__(self, /) -> None: ...
 
 class IndexExpression(Generic[_BoolT_co]):
+    __slots__ = ("maketuple",)
+
     maketuple: _BoolT_co
     def __init__(self, /, maketuple: _BoolT_co) -> None: ...
     #
diff --git a/src/numpy-stubs/ma/extras.pyi b/src/numpy-stubs/ma/extras.pyi
index a5ec3259..cc5e9d44 100644
--- a/src/numpy-stubs/ma/extras.pyi
+++ b/src/numpy-stubs/ma/extras.pyi
@@ -1,5 +1,5 @@
 from _typeshed import Incomplete
-from typing import Final
+from typing import Final, final
 from typing_extensions import override
 
 import _numtype as _nt
@@ -80,6 +80,8 @@ class _fromnxfunction_allargs(_fromnxfunction):
     def __call__(self, *args: Incomplete, **params: Incomplete) -> Incomplete: ...
 
 class MAxisConcatenator(AxisConcatenator):
+    __slots__ = ()
+
     @staticmethod
     @override
     def concatenate(arrays: Incomplete, axis: int = 0) -> Incomplete: ...  # type: ignore[override]  # pyright: ignore[reportIncompatibleMethodOverride]
@@ -87,7 +89,10 @@ class MAxisConcatenator(AxisConcatenator):
     @override
     def makemat(cls, arr: Incomplete) -> Incomplete: ...  # type: ignore[override]  # pyright: ignore[reportIncompatibleVariableOverride]
 
+@final
 class mr_class(MAxisConcatenator):
+    __slots__ = ()
+
     def __init__(self) -> None: ...
 
 def count_masked(arr: Incomplete, axis: Incomplete = ...) -> Incomplete: ...