diff --git a/pylabrobot/liquid_handling/liquid_handler.py b/pylabrobot/liquid_handling/liquid_handler.py
index 14a5876c92..0175837457 100644
--- a/pylabrobot/liquid_handling/liquid_handler.py
+++ b/pylabrobot/liquid_handling/liquid_handler.py
@@ -1001,7 +1001,7 @@ async def dispense(
 
     for resource in resources:
       if isinstance(resource.parent, Plate) and resource.parent.has_lid():
-        raise ValueError("Dispensing to plate with lid")
+        raise ValueError("Aspirating from a well with a lid is not supported.")
 
     assert len(vols) == len(offsets) == len(flow_rates) == len(liquid_height)
 
diff --git a/pylabrobot/resources/filter.py b/pylabrobot/resources/filter.py
new file mode 100644
index 0000000000..4a64c08724
--- /dev/null
+++ b/pylabrobot/resources/filter.py
@@ -0,0 +1,81 @@
+from typing import Optional, Union
+
+from pylabrobot.liquid_handling.liquid_handler import LiquidHandler
+from pylabrobot.resources.carrier import ResourceHolder
+from pylabrobot.resources.coordinate import Coordinate
+from pylabrobot.resources.plate import Plate
+from pylabrobot.resources.resource import Resource
+
+
+class Filter(Resource):
+  """Filter for plates for use in filtering cells before flow cytometry."""
+
+  filter_dispense_offset = Coordinate(
+    0, 0, 7
+  )  # height to pipette through filter (required pressure on filter)
+
+  def __init__(
+    self,
+    name: str,
+    size_x: float,
+    size_y: float,
+    size_z: float,
+    category: str = "filter",
+    model: Optional[str] = None,
+  ):
+    super().__init__(
+      name=name,
+      size_x=size_x,
+      size_y=size_y,
+      size_z=size_z,
+      category=category,
+      model=model,
+    )
+
+  async def move_filter(
+    self,
+    lh: LiquidHandler,
+    to_dest: Union[Plate, ResourceHolder, Coordinate],
+    arm: str = "core",
+    **kwargs,
+  ):
+    """move filter from CarrierSite to a Plate using core grippers (faster) or iSWAP (slower)"""
+    await lh.move_resource(
+      resource=self,
+      to=to_dest,
+      use_arm=arm,
+      pickup_distance_from_top=15,
+      core_grip_strength=20,
+      return_core_gripper=True,
+      **kwargs,
+    )
+
+  async def dispense_through_filter(
+    self, indices: list[int], volume: float, lh: LiquidHandler, **disp_kwargs
+  ):
+    assert isinstance(self.parent, Plate), "Filter must be placed on a plate to be pipetted."
+
+    offsets = disp_kwargs.get("offsets", self.filter_dispense_offset)
+    if not isinstance(offsets, Coordinate):
+      raise ValueError("Offsets must be a Coordinate.")
+
+    defaults = {
+      "offsets": [offsets + self.filter_dispense_offset] * len(indices)
+      if isinstance(offsets, Coordinate)
+      else [offsets] * len(indices),
+      "transport_air_volume": 5,
+      "swap_speed": 100,
+      "minimum_traverse_height_at_beginning_of_a_command": self.parent.get_absolute_location(
+        "c", "c", "t"
+      ).z
+      + 20,
+      "min_z_endpos": self.parent.get_absolute_location("c", "c", "t").z + 20,
+    }
+
+    disp_params = {**defaults, **{k: v for k, v in disp_kwargs.items() if k in defaults}}
+
+    await lh.dispense([self.parent[i][0] for i in indices], [volume] * len(indices), **disp_params)
+
+
+def RetroFilterv4(name: str) -> Filter:
+  return Filter(name=name, size_x=129, size_y=88, size_z=19.7)
diff --git a/pylabrobot/resources/retro_filter/__init__.py b/pylabrobot/resources/retro_filter/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/pylabrobot/resources/retro_filter/retro_filter.md b/pylabrobot/resources/retro_filter/retro_filter.md
new file mode 100644
index 0000000000..b514d6cfaa
--- /dev/null
+++ b/pylabrobot/resources/retro_filter/retro_filter.md
@@ -0,0 +1,23 @@
+# Retro Filter V4
+
+<img src="retro_filter.png" width="800" />
+
+Designed for flow cytometry prep.
+
+## Usage Instructions
+
+1. Lay **40–80 µm filter cloth** between the upper and lower portions.
+2. Snap the filter assembly shut.
+3. Lay scissors flush against the top-bottom interface.
+4. **Cut the filter cloth close** to the printed parts to avoid any excess that could obstruct robotic handling.
+5. The filter is ready for **single-use**.
+
+> **Tip**: For a reusable filtration assembly, purchase **80 µm steel mesh** from Component Supply.
+
+
+### [OnShape doc](https://cad.onshape.com/documents/c9c3cf6b64034d54f966eda5/w/fed83636389b833df37c2dac/e/80426a2258abe186fc00e172?renderMode=0&uiState=6768d74c1ea3896154236237)
+
+
+<p align="left">
+  <img src="../../docs/img/used_by/retrobio.webp" alt="RetroBio Logo" width="100"/>
+</p>
diff --git a/pylabrobot/resources/retro_filter/retro_filter.png b/pylabrobot/resources/retro_filter/retro_filter.png
new file mode 100644
index 0000000000..836974dbd6
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diff --git a/pylabrobot/resources/retro_filter/retro_filter_lower.stl b/pylabrobot/resources/retro_filter/retro_filter_lower.stl
new file mode 100644
index 0000000000..1231bef333
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diff --git a/pylabrobot/resources/retro_filter/retro_filter_upper.stl b/pylabrobot/resources/retro_filter/retro_filter_upper.stl
new file mode 100644
index 0000000000..72de058012
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