diff --git a/spec.bs b/spec.bs
index 0904a67..54eea7a 100644
--- a/spec.bs
+++ b/spec.bs
@@ -983,7 +983,17 @@ A fenced frame config is a [=struct=] with the following [=str
: embedder shared storage context
:: null, or a [=string=]
+
+ : is ad component
+ :: A [=boolean=]. Defaulting to false.
+
+ Note: When true, this [=fenced frame config=] reprsents an ad component. An ad component can be
+ used to construct ads composed of multiple pieces. See the Protected
+ Audience explainer. For an ad component, event reporting is handled differently. See the Fenced
+ Frame Ads Reporting explainer that describes this.
The [=fenced frame config instance=] [=struct=]
@@ -1026,6 +1036,9 @@ A fenced frame config instance is a [=struct=] with the follow
: embedder shared storage context
:: null, or a [=string=]
+
+ : is ad component
+ :: A [=boolean=], initially false.
@@ -1110,6 +1123,9 @@ A fenced frame config instance is a [=struct=] with the follow
: [=fenced frame config instance/embedder shared storage context=]
:: |config|'s [=fenced frame config/embedder shared storage context=]
+
+ : [=fenced frame config instance/is ad component=]
+ :: |config|'s [=fenced frame config/is ad component=]
Each [=browsing context=] has a fenced frame config instance,