diff --git a/packages/core/models/audioClip.model.ts b/packages/core/models/audioClip.model.ts
deleted file mode 100644
index 95e32d1..0000000
--- a/packages/core/models/audioClip.model.ts
+++ /dev/null
@@ -1,12 +0,0 @@
-import { ObjectId } from "mongodb";
-
-export default class AudioClip {
-  constructor(
-    public _id: ObjectId,
-
-    public url: string,
-
-    public createdDate: Date = new Date(),
-    public duration?: number
-  ) {}
-}
diff --git a/packages/core/models/content.model.ts b/packages/core/models/content.model.ts
index ce17a43..4d8a9e6 100644
--- a/packages/core/models/content.model.ts
+++ b/packages/core/models/content.model.ts
@@ -1,7 +1,7 @@
 import { ObjectId } from 'mongodb';
 
 export interface IContent {
-  id?: string;
+  id?: ObjectId;
 
   creatorUserId: string;
   contentUrl: string; // remote resource of file/media
@@ -22,7 +22,8 @@ export class ContentBlock implements IContent {
 
     public createdDate = new Date(),
 
-    public id?: string,
+    public metadata?: object,
+    public id?: ObjectId,
   ) {}
 }
 
diff --git a/packages/core/models/conversation.model.ts b/packages/core/models/conversation.model.ts
index 3050bed..365d0f2 100644
--- a/packages/core/models/conversation.model.ts
+++ b/packages/core/models/conversation.model.ts
@@ -1,3 +1,4 @@
+import { ObjectId } from 'mongodb';
 import User from './user.model';
 
 export default class Conversation {
@@ -23,7 +24,7 @@ export default class Conversation {
     public lastUpdatedDate = new Date(),
     public createdDate = new Date(),
 
-    public id?: string,
+    public id?: ObjectId,
   ) {}
 }