diff --git a/quiche/common/quiche_protocol_flags_list.h b/quiche/common/quiche_protocol_flags_list.h
index 9e84b68..7477f87 100644
--- a/quiche/common/quiche_protocol_flags_list.h
+++ b/quiche/common/quiche_protocol_flags_list.h
@@ -127,10 +127,19 @@
     "probes, in milliseconds.")
 
 QUICHE_PROTOCOL_FLAG(
+    double, quic_bbr2_default_probe_rtt_inflight_target_bdp_fraction, 0.5,
+    "The default fraction to adjust the target in flight BDP during "
+    "PROBE_RTT phase.")
+
+QUICHE_PROTOCOL_FLAG(
     int32_t, quic_bbr2_default_probe_rtt_period_ms, 10000,
     "The default period for entering PROBE_RTT, in milliseconds.")
 
 QUICHE_PROTOCOL_FLAG(
+    int32_t, quic_bbr2_default_probe_rtt_duration_ms, 200,
+    "The default time to spend in PROBE_RTT mode, in milliseconds.")
+
+QUICHE_PROTOCOL_FLAG(
     double, quic_bbr2_default_loss_threshold, 0.02,
     "The default loss threshold for QUIC BBRv2, should be a value "
     "between 0 and 1.")
diff --git a/quiche/quic/core/congestion_control/bbr2_misc.h b/quiche/quic/core/congestion_control/bbr2_misc.h
index c621983..15dcd53 100644
--- a/quiche/quic/core/congestion_control/bbr2_misc.h
+++ b/quiche/quic/core/congestion_control/bbr2_misc.h
@@ -158,10 +158,12 @@
   /*
    * PROBE_RTT parameters.
    */
-  float probe_rtt_inflight_target_bdp_fraction = 0.5;
+  float probe_rtt_inflight_target_bdp_fraction =
+      GetQuicFlag(quic_bbr2_default_probe_rtt_inflight_target_bdp_fraction);
   QuicTime::Delta probe_rtt_period = QuicTime::Delta::FromMilliseconds(
       GetQuicFlag(quic_bbr2_default_probe_rtt_period_ms));
-  QuicTime::Delta probe_rtt_duration = QuicTime::Delta::FromMilliseconds(200);
+  QuicTime::Delta probe_rtt_duration = QuicTime::Delta::FromMilliseconds(
+      GetQuicFlag(quic_bbr2_default_probe_rtt_duration_ms));
 
   /*
    * Parameters used by multiple modes.