diff --git a/data-structures.md b/data-structures.md
index 506c58e92..89b9b13ca 100644
--- a/data-structures.md
+++ b/data-structures.md
@@ -231,10 +231,15 @@ type Bitfield Bytes
 
 ### SectorSet
 
-{{% notice todo %}}
-Define me
-{{% /notice %}}
+```sh
+type SectorSet {UInt:SectorMetaData}<AMT>
+
+type SectorMetaData struct {
+    ## TODO: define these fields
+}
+```
 
+The `AMT` format can be found [here](https://github.com/ipld/specs/pull/137).
 
 ### SealProof