diff --git a/docs/how-to/pyserial-migration.md b/docs/how-to/pyserial-migration.md
index f99ad81..9a92606 100644
--- a/docs/how-to/pyserial-migration.md
+++ b/docs/how-to/pyserial-migration.md
@@ -85,6 +85,26 @@ with serialx.serial_for_url("/dev/ttyUSB0", baudrate=115200) as serial:
 
 There is no equivalent for async code because the default `create_serial_connection` and `open_serial_connection` functions already transparently accept URIs.
 
+## Constants
+pyserial exposes parity, stop bit, and byte size settings as module-level constants (`serial.PARITY_NONE`, `serial.STOPBITS_ONE`, etc.). serialx replaces them with the `Parity` and `StopBits` enums. Properties like `serial.parity` and `serial.stopbits` now return enum members instead of raw strings or numbers.
+
+| Old Name                    | New Name                      |
+| ---                         | ---                           |
+| `PARITY_NONE`               | `Parity.NONE`                 |
+| `PARITY_EVEN`               | `Parity.EVEN`                 |
+| `PARITY_ODD`                | `Parity.ODD`                  |
+| `PARITY_MARK`               | `Parity.MARK`                 |
+| `PARITY_SPACE`              | `Parity.SPACE`                |
+| `STOPBITS_ONE`              | `StopBits.ONE`                |
+| `STOPBITS_ONE_POINT_FIVE`   | `StopBits.ONE_POINT_FIVE`     |
+| `STOPBITS_TWO`              | `StopBits.TWO`                |
+| `FIVEBITS`                  | `5`                           |
+| `SIXBITS`                   | `6`                           |
+| `SEVENBITS`                 | `7`                           |
+| `EIGHTBITS`                 | `8`                           |
+
+Migrate to the enum members. `Parity` is a `str` enum and `StopBits` is a `float` enum, so any lingering comparisons against raw values (`parity == "N"`, `stopbits == 1`) still hold during the transition. These direct comparisons should be migrated to use the enum members instead of assuming their values.
+
 ## Exceptions
 pyserial re-raises all errors as `serial.SerialException`, including OS-level failures and timeouts. serialx raises native exceptions directly so callers can handle them granularly:
 
diff --git a/serialx/__init__.py b/serialx/__init__.py
index 2cba6cc..8e482d0 100644
--- a/serialx/__init__.py
+++ b/serialx/__init__.py
@@ -25,12 +25,17 @@
 from .compat import (
     CR,
     EIGHTBITS,
+    FIVEBITS,
     LF,
     PARITY_EVEN,
+    PARITY_MARK,
     PARITY_NONE,
     PARITY_ODD,
+    PARITY_SPACE,
     SEVENBITS,
+    SIXBITS,
     STOPBITS_ONE,
+    STOPBITS_ONE_POINT_FIVE,
     STOPBITS_TWO,
     SerialTimeoutException,
 )
@@ -59,12 +64,17 @@
     "StopBits",
     # Compatibility with pyserial
     "SerialTimeoutException",
-    "EIGHTBITS",
+    "FIVEBITS",
+    "SIXBITS",
     "SEVENBITS",
+    "EIGHTBITS",
     "PARITY_NONE",
     "PARITY_EVEN",
     "PARITY_ODD",
+    "PARITY_MARK",
+    "PARITY_SPACE",
     "STOPBITS_ONE",
+    "STOPBITS_ONE_POINT_FIVE",
     "STOPBITS_TWO",
     "CR",
     "LF",
diff --git a/serialx/common.py b/serialx/common.py
index 02a11ed..273466e 100644
--- a/serialx/common.py
+++ b/serialx/common.py
@@ -176,7 +176,7 @@ class UnknownUriScheme(SerialException):
     """Raised when a URI scheme has no registered handler."""
 
 
-class StopBits(Enum):
+class StopBits(float, Enum):
     """Stop bits configuration."""
 
     ONE = 1
diff --git a/serialx/compat.py b/serialx/compat.py
index 0e5537c..ada2869 100644
--- a/serialx/compat.py
+++ b/serialx/compat.py
@@ -4,14 +4,19 @@
 
 SerialTimeoutException = TimeoutError
 
-EIGHTBITS = 8
+FIVEBITS = 5
+SIXBITS = 6
 SEVENBITS = 7
+EIGHTBITS = 8
 
 PARITY_NONE = Parity.NONE
 PARITY_EVEN = Parity.EVEN
 PARITY_ODD = Parity.ODD
+PARITY_MARK = Parity.MARK
+PARITY_SPACE = Parity.SPACE
 
 STOPBITS_ONE = StopBits.ONE
+STOPBITS_ONE_POINT_FIVE = StopBits.ONE_POINT_FIVE
 STOPBITS_TWO = StopBits.TWO
 
 CR = b"\r"
diff --git a/tests/test_pyserial_compat.py b/tests/test_pyserial_compat.py
index 3ff1711..ec823b7 100644
--- a/tests/test_pyserial_compat.py
+++ b/tests/test_pyserial_compat.py
@@ -11,7 +11,23 @@
         allow_module_level=True,
     )
 
-from serialx import Parity, Serial, SerialPortInfo
+from serialx import (
+    EIGHTBITS,
+    FIVEBITS,
+    PARITY_EVEN,
+    PARITY_MARK,
+    PARITY_NONE,
+    PARITY_ODD,
+    PARITY_SPACE,
+    SEVENBITS,
+    SIXBITS,
+    STOPBITS_ONE,
+    STOPBITS_ONE_POINT_FIVE,
+    STOPBITS_TWO,
+    Parity,
+    Serial,
+    SerialPortInfo,
+)
 from serialx.tools.list_ports import comports, grep
 from serialx.tools.list_ports_common import ListPortInfo
 from tests.common import SerialPair
@@ -143,6 +159,24 @@ def test_compat_do_not_open(serial_pair: SerialPair) -> None:
     assert not s.is_open
 
 
+def test_compat_constants() -> None:
+    """Test that pyserial module-level constants are re-exported with correct values."""
+    assert FIVEBITS == 5
+    assert SIXBITS == 6
+    assert SEVENBITS == 7
+    assert EIGHTBITS == 8
+
+    assert PARITY_NONE == "N"
+    assert PARITY_EVEN == "E"
+    assert PARITY_ODD == "O"
+    assert PARITY_MARK == "M"
+    assert PARITY_SPACE == "S"
+
+    assert STOPBITS_ONE == 1  # type: ignore[comparison-overlap]
+    assert STOPBITS_ONE_POINT_FIVE == 1.5
+    assert STOPBITS_TWO == 2
+
+
 def test_compat_tools_module() -> None:
     """Test that serialx.tools.list_ports provides pyserial-compatible API."""
     # comports is list_serial_ports