diff --git a/pyproject.toml b/pyproject.toml
index fc3dab1..992c416 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,7 +19,7 @@ classifiers = [
     "Topic :: Scientific/Engineering :: GIS",
     "Typing :: Typed",
 ]
-version = "0.2.1"
+version = "0.3.0"
 dependencies = ["pydantic>=2.3,<3"]
 
 [project.optional-dependencies]
diff --git a/src/edr_pydantic/extent.py b/src/edr_pydantic/extent.py
index be808e4..cb5dfd6 100644
--- a/src/edr_pydantic/extent.py
+++ b/src/edr_pydantic/extent.py
@@ -1,5 +1,6 @@
 from typing import List
 from typing import Optional
+from typing import Union
 
 from pydantic import AwareDatetime
 
@@ -26,10 +27,10 @@ class Vertical(EdrBaseModel):
 
 
 class Custom(EdrBaseModel):
-    interval: List[str]
     id: str
-    values: List[str]
-    reference: Optional[str] = None
+    interval: List[List[Union[str, float]]]
+    values: Optional[List[Union[str, float]]] = None
+    reference: str
 
 
 class Extent(EdrBaseModel):
diff --git a/tests/test_data/doc-example-extent.json b/tests/test_data/doc-example-extent.json
new file mode 100644
index 0000000..61548e3
--- /dev/null
+++ b/tests/test_data/doc-example-extent.json
@@ -0,0 +1,61 @@
+{
+    "spatial": {
+        "bbox": [
+            [
+                -180.0,
+                -90.0,
+                180.0,
+                90.0
+            ]
+        ],
+        "crs": "GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]],AUTHORITY[\"EPSG\",\"4326\"]]"
+    },
+    "temporal": {
+        "interval": [
+            [
+                "2017-06-14T00:00:00Z",
+                "2017-06-14T12:00:00Z"
+            ]
+        ],
+        "values": [
+            "2017-06-14T00:00:00Z",
+            "2017-06-14T06:00:00Z",
+            "2017-06-14T12:00:00Z",
+            "2017-06-14T18:00:00Z"
+        ],
+        "trs": "TIMECRS[\"DateTime\",TDATUM[\"Gregorian Calendar\"],CS[TemporalDateTime,1],AXIS[\"Time (T)\",future]]"
+    },
+    "custom": [
+        {
+            "id": "realisations",
+            "interval": [
+                [
+                    1.0,
+                    50.0
+                ]
+            ],
+            "values": [
+                "R50/1/1"
+            ],
+            "reference": "Ensemble members"
+        },
+        {
+            "id": "icao_ids",
+            "interval": [
+                [
+                    "EB",
+                    "EB"
+                ]
+            ],
+            "values": [
+                "EBAW",
+                "EBBR",
+                "EBBR",
+                "EBKT",
+                "EBLG",
+                "EBOS"
+            ],
+            "reference": "https://en.wikipedia.org/wiki/ICAO_airport_code"
+        }
+    ]
+}
diff --git a/tests/test_edr.py b/tests/test_edr.py
index 0376f71..c68e4ac 100644
--- a/tests/test_edr.py
+++ b/tests/test_edr.py
@@ -5,6 +5,7 @@
 from edr_pydantic.capabilities import LandingPageModel
 from edr_pydantic.collections import Collections
 from edr_pydantic.collections import Instance
+from edr_pydantic.extent import Extent
 from edr_pydantic.unit import Unit
 from pydantic import ValidationError
 
@@ -13,6 +14,7 @@
     ("doc-example-collections.json", Collections),
     ("simple-instance.json", Instance),
     ("landing-page.json", LandingPageModel),
+    ("doc-example-extent.json", Extent),
 ]