diff --git a/addons/io_scene_swbf_msh/msh_model.py b/addons/io_scene_swbf_msh/msh_model.py
index 0dc75ee..d97918f 100644
--- a/addons/io_scene_swbf_msh/msh_model.py
+++ b/addons/io_scene_swbf_msh/msh_model.py
@@ -18,7 +18,7 @@ class CollisionPrimitiveShape(Enum):
     # ELLIPSOID = 1
     CYLINDER = 2
     # MESH = 3
-    CUBE = 4
+    BOX = 4
 
 @dataclass
 class ModelTransform:
@@ -47,10 +47,10 @@ class GeometrySegment:
 class CollisionPrimitive:
     """ Class representing a 'SWCI' section in a .msh file. """
 
-    collision_primitive_shape: CollisionPrimitiveShape
-    radius: float
-    height: float
-    length: float
+    shape: CollisionPrimitiveShape = CollisionPrimitiveShape.SPHERE
+    radius: float = 0.0
+    height: float = 0.0
+    length: float = 0.0
 
 @dataclass
 class Model:
diff --git a/addons/io_scene_swbf_msh/msh_model_gather.py b/addons/io_scene_swbf_msh/msh_model_gather.py
index fbf014a..221731c 100644
--- a/addons/io_scene_swbf_msh/msh_model_gather.py
+++ b/addons/io_scene_swbf_msh/msh_model_gather.py
@@ -2,6 +2,7 @@
     Model objects. """
 
 import bpy
+import math
 from typing import List, Set, Dict, Tuple
 from itertools import zip_longest
 from .msh_model import *
@@ -44,6 +45,9 @@ def gather_models() -> List[Model]:
             mesh_scale = convert_vector_space(get_object_worldspace_scale(obj))
             scale_segments(mesh_scale, model.geometry)
 
+        if get_is_collision_primitive(obj):
+            model.collisionprimitive = get_collision_primitive(obj)
+
         models_list.append(model)
 
     return models_list
@@ -163,6 +167,56 @@ def get_is_model_hidden(obj: bpy.types.Object) -> bool:
 
     return False
 
+def get_is_collision_primitive(obj: bpy.types.Object) -> bool:
+    """ Gets if a Blender object represents a collision primitive. """
+
+    name = obj.name.lower()
+
+    return name.startswith("p_")
+
+def get_collision_primitive(obj: bpy.types.Object) -> CollisionPrimitive:
+    """ Gets the CollisionPrimitive of an object or raises an error if
+        it can't. """
+
+    primitive = CollisionPrimitive()
+    primitive.shape = get_collision_primitive_shape(obj)
+
+    if primitive.shape == CollisionPrimitiveShape.SPHERE:
+        # Tolerate a 5% difference to account for icospheres with 2 subdivisions.
+        if not (math.isclose(obj.dimensions[0], obj.dimensions[1], rel_tol=0.05) and
+                math.isclose(obj.dimensions[0], obj.dimensions[2], rel_tol=0.05)):
+            raise RuntimeError(f"Object '{obj.name}' is being used as a sphere collision "
+                               f"primitive but it's dimensions are not uniform!")
+
+        primitive.radius = max(obj.dimensions[0], obj.dimensions[1], obj.dimensions[2]) * 0.5
+    elif primitive.shape == CollisionPrimitiveShape.CYLINDER:
+        if not math.isclose(obj.dimensions[0], obj.dimensions[1], rel_tol=0.001):
+            raise RuntimeError(f"Object '{obj.name}' is being used as a cylinder collision "
+                               f"primitive but it's X and Y dimensions are not uniform!")
+        primitive.radius = obj.dimensions[0] * 0.5
+        primitive.height = obj.dimensions[2] * 0.5
+    elif primitive.shape == CollisionPrimitiveShape.BOX:
+        primitive.radius = obj.dimensions[0] * 0.5
+        primitive.height = obj.dimensions[2] * 0.5
+        primitive.length = obj.dimensions[1] * 0.5
+
+    return primitive
+
+def get_collision_primitive_shape(obj: bpy.types.Object) -> CollisionPrimitiveShape:
+    """ Gets the CollisionPrimitiveShape of an object or raises an error if
+        it can't. """
+
+    name = obj.name.lower()
+
+    if "sphere" in name or "sphr" in name or "spr" in name:
+        return CollisionPrimitiveShape.SPHERE
+    if "cylinder" in name or "cyln" in name or "cyl" in name:
+        return CollisionPrimitiveShape.CYLINDER
+    if "box" in name:
+        return CollisionPrimitiveShape.BOX
+
+    raise RuntimeError(f"Object '{obj.name}' has no primitive type specified in it's name!")
+
 def convert_vector_space(vec: Vector) -> Vector:
     return Vector(vec.xzy)
 
diff --git a/addons/io_scene_swbf_msh/msh_scene_save.py b/addons/io_scene_swbf_msh/msh_scene_save.py
index bb14db0..71914a0 100644
--- a/addons/io_scene_swbf_msh/msh_scene_save.py
+++ b/addons/io_scene_swbf_msh/msh_scene_save.py
@@ -124,7 +124,12 @@ def _write_modl(modl: Writer, model: Model, index: int, material_index: Dict[str
                 with geom.create_child("SEGM") as segm:
                     _write_segm(segm, segment, material_index)
 
-    # TODO: Collision Primitive
+    if model.collisionprimitive is not None:
+        with modl.create_child("SWCI") as swci:
+            swci.write_u32(model.collisionprimitive.shape.value)
+            swci.write_f32(model.collisionprimitive.radius)
+            swci.write_f32(model.collisionprimitive.height)
+            swci.write_f32(model.collisionprimitive.length)
 
 def _write_tran(tran: Writer, transform: ModelTransform):
     tran.write_f32(1.0, 1.0, 1.0) # Scale, ignored by modelmunge