diff --git a/quic/api/test/QuicTransportFunctionsTest.cpp b/quic/api/test/QuicTransportFunctionsTest.cpp
index 37202bd54..a8be26edd 100644
--- a/quic/api/test/QuicTransportFunctionsTest.cpp
+++ b/quic/api/test/QuicTransportFunctionsTest.cpp
@@ -1683,7 +1683,7 @@ TEST_F(QuicTransportFunctionsTest, TestStreamDetailsControlPacket) {
   ASSERT_EQ(1, conn->outstandings.packets.size());
   const auto& detailsPerStream =
       getFirstOutstandingPacket(*conn, PacketNumberSpace::AppData)
-          ->metadata.detailsPerStream.getDetails();
+          ->metadata.detailsPerStream;
   EXPECT_EQ(0, detailsPerStream.size());
 }
 
@@ -1707,9 +1707,9 @@ TEST_F(QuicTransportFunctionsTest, TestStreamDetailsAppDataPacketSingleStream) {
   ASSERT_EQ(1, conn->outstandings.packets.size());
   auto detailsPerStream =
       getFirstOutstandingPacket(*conn, PacketNumberSpace::AppData)
-          ->metadata.detailsPerStream.getDetails();
+          ->metadata.detailsPerStream;
   EXPECT_EQ(1, detailsPerStream.size());
-  auto streamDetail = detailsPerStream[stream->id];
+  auto streamDetail = detailsPerStream.at(stream->id);
   EXPECT_EQ(false, streamDetail.finObserved);
   EXPECT_EQ(10, streamDetail.streamBytesSent);
   EXPECT_EQ(10, streamDetail.newStreamBytesSent);
@@ -1742,9 +1742,9 @@ TEST_F(
   ASSERT_EQ(1, conn->outstandings.packets.size());
   auto detailsPerStream =
       getFirstOutstandingPacket(*conn, PacketNumberSpace::AppData)
-          ->metadata.detailsPerStream.getDetails();
+          ->metadata.detailsPerStream;
   EXPECT_EQ(1, detailsPerStream.size());
-  auto streamDetail = detailsPerStream[stream->id];
+  auto streamDetail = detailsPerStream.at(stream->id);
   EXPECT_EQ(true, streamDetail.finObserved);
   EXPECT_EQ(15, streamDetail.streamBytesSent);
   EXPECT_EQ(15, streamDetail.newStreamBytesSent);
@@ -1777,9 +1777,9 @@ TEST_F(
   // The first outstanding packet is the one with new data
   auto detailsPerStream =
       getFirstOutstandingPacket(*conn, PacketNumberSpace::AppData)
-          ->metadata.detailsPerStream.getDetails();
+          ->metadata.detailsPerStream;
   EXPECT_EQ(1, detailsPerStream.size());
-  auto streamDetail = detailsPerStream[stream->id];
+  auto streamDetail = detailsPerStream.at(stream->id);
   EXPECT_EQ(false, streamDetail.finObserved);
   EXPECT_EQ(frame1Len, streamDetail.streamBytesSent);
   EXPECT_EQ(frame1Len, streamDetail.newStreamBytesSent);
@@ -1801,9 +1801,9 @@ TEST_F(
 
   // The second outstanding packet is the one with retransmit data
   detailsPerStream = getLastOutstandingPacket(*conn, PacketNumberSpace::AppData)
-                         ->metadata.detailsPerStream.getDetails();
+                         ->metadata.detailsPerStream;
   EXPECT_EQ(1, detailsPerStream.size());
-  streamDetail = detailsPerStream[stream->id];
+  streamDetail = detailsPerStream.at(stream->id);
   EXPECT_EQ(false, streamDetail.finObserved);
   EXPECT_EQ(frame1Len, streamDetail.streamBytesSent);
   EXPECT_EQ(0, streamDetail.newStreamBytesSent);
@@ -1831,9 +1831,9 @@ TEST_F(
 
   // The third outstanding packet will have both new and retransmitted data.
   detailsPerStream = getLastOutstandingPacket(*conn, PacketNumberSpace::AppData)
-                         ->metadata.detailsPerStream.getDetails();
+                         ->metadata.detailsPerStream;
   EXPECT_EQ(1, detailsPerStream.size());
-  streamDetail = detailsPerStream[stream->id];
+  streamDetail = detailsPerStream.at(stream->id);
   EXPECT_EQ(false, streamDetail.finObserved);
   EXPECT_EQ(frame1Len + frame2Len, streamDetail.streamBytesSent);
   EXPECT_EQ(frame2Len, streamDetail.newStreamBytesSent);
@@ -1856,9 +1856,9 @@ TEST_F(
 
   // The forth outstanding packet will have only retransmit data.
   detailsPerStream = getLastOutstandingPacket(*conn, PacketNumberSpace::AppData)
-                         ->metadata.detailsPerStream.getDetails();
+                         ->metadata.detailsPerStream;
   EXPECT_EQ(1, detailsPerStream.size());
-  streamDetail = detailsPerStream[stream->id];
+  streamDetail = detailsPerStream.at(stream->id);
   EXPECT_EQ(false, streamDetail.finObserved);
   EXPECT_EQ(frame1Len + frame2Len, streamDetail.streamBytesSent);
   EXPECT_EQ(0, streamDetail.newStreamBytesSent);
@@ -1900,10 +1900,10 @@ TEST_F(
   ASSERT_EQ(1, conn->outstandings.packets.size());
   auto detailsPerStream =
       getFirstOutstandingPacket(*conn, PacketNumberSpace::AppData)
-          ->metadata.detailsPerStream.getDetails();
+          ->metadata.detailsPerStream;
   EXPECT_EQ(2, detailsPerStream.size());
-  auto stream1Detail = detailsPerStream[stream1Id];
-  auto stream2Detail = detailsPerStream[stream2Id];
+  auto stream1Detail = detailsPerStream.at(stream1Id);
+  auto stream2Detail = detailsPerStream.at(stream2Id);
 
   EXPECT_EQ(false, stream1Detail.finObserved);
   EXPECT_EQ(5, stream1Detail.streamBytesSent);
diff --git a/quic/state/OutstandingPacket.h b/quic/state/OutstandingPacket.h
index 8dc4c9adf..98858eedd 100644
--- a/quic/state/OutstandingPacket.h
+++ b/quic/state/OutstandingPacket.h
@@ -45,23 +45,22 @@ struct OutstandingPacketMetadata {
   // tracks the number of writes on this socket.
   uint64_t writeCount{0};
 
-  // Structure used to hold information about each stream with frames in packet
-  class DetailsPerStream {
+  struct StreamDetails {
+    template <class T>
+    using IntervalSetVec = SmallVec<T, 2 /* stack size */, uint16_t>;
+    using StreamIntervals = IntervalSet<uint64_t, 1, IntervalSetVec>;
+    StreamIntervals streamIntervals;
+
+    bool finObserved{false};
+    uint64_t streamBytesSent{0};
+    uint64_t newStreamBytesSent{0};
+    folly::Optional<uint64_t> maybeFirstNewStreamByteOffset;
+  };
+
+  class DetailsPerStream : private folly::F14FastMap<StreamId, StreamDetails> {
    public:
-    struct StreamDetails {
-      template <class T>
-      using IntervalSetVec = SmallVec<T, 2 /* stack size */, uint16_t>;
-      using StreamIntervals = IntervalSet<uint64_t, 1, IntervalSetVec>;
-      StreamIntervals streamIntervals;
-
-      bool finObserved{false};
-      uint64_t streamBytesSent{0};
-      uint64_t newStreamBytesSent{0};
-      folly::Optional<uint64_t> maybeFirstNewStreamByteOffset;
-    };
-
     void addFrame(const WriteStreamFrame& frame, const bool newData) {
-      auto ret = detailsPerStream.emplace(
+      auto ret = emplace(
           std::piecewise_construct,
           std::make_tuple(frame.streamId),
           std::make_tuple());
@@ -87,13 +86,26 @@ struct OutstandingPacketMetadata {
       }
     }
 
-    FOLLY_NODISCARD const folly::F14FastMap<StreamId, StreamDetails>&
-    getDetails() const {
-      return detailsPerStream;
+    [[nodiscard]] auto at(StreamId id) const {
+      return folly::F14FastMap<StreamId, StreamDetails>::at(id);
     }
 
-   private:
-    folly::F14FastMap<StreamId, StreamDetails> detailsPerStream;
+    [[nodiscard]] auto begin() const {
+      return cbegin();
+    }
+
+    [[nodiscard]] auto end() const {
+      return cend();
+    }
+
+    using folly::F14FastMap<StreamId, StreamDetails>::cbegin;
+    using folly::F14FastMap<StreamId, StreamDetails>::cend;
+    using folly::F14FastMap<StreamId, StreamDetails>::const_iterator;
+    using folly::F14FastMap<StreamId, StreamDetails>::empty;
+    using folly::F14FastMap<StreamId, StreamDetails>::find;
+    using folly::F14FastMap<StreamId, StreamDetails>::mapped_type;
+    using folly::F14FastMap<StreamId, StreamDetails>::size;
+    using folly::F14FastMap<StreamId, StreamDetails>::value_type;
   };
 
   // Details about each stream with frames in this packet