diff --git a/tools/bench_a2_fast.cpp b/tools/bench_a2_fast.cpp
index 2dcaff1..4057503 100644
--- a/tools/bench_a2_fast.cpp
+++ b/tools/bench_a2_fast.cpp
@@ -6,7 +6,12 @@
 // Runs both over the same audio, reports median wall time + real-time factor.
 //
 // Usage:
-//   bench_a2_fast [--buffer N] [--seconds S] [--iters I] <model.nam> [<model.nam> ...]
+//   bench_a2_fast [--buffer N] [--seconds S] [--iters I] [--slim V] <model.nam> [<model.nam> ...]
+//
+// A model may be a plain WaveNet .nam or a SlimmableContainer .nam (e.g. an A2 file
+// bundling A2-Full + A2-Lite submodels). For a container, --slim V (0.0-1.0) selects the
+// submodel exactly as ContainerModel::SetSlimmableSize would (first submodel whose
+// max_value exceeds V, else the last); the selected submodel is then benched fast vs generic.
 //
 // Only compiled when NAM_ENABLE_A2_FAST is defined.
 
@@ -44,9 +49,13 @@ struct Options
   int buffer_size = 64;
   double seconds = 2.0;
   int iterations = 10;
+  double slim = 1.0; // SlimmableContainer selector; defaults to full size (last submodel)
+  bool has_slim = false;
   std::vector<std::string> model_paths;
 };
 
+const char* kUsage = "Usage: bench_a2_fast [--buffer N] [--seconds S] [--iters I] [--slim V] <model.nam> ...\n";
+
 Options parse_args(int argc, char** argv)
 {
   Options o;
@@ -59,9 +68,19 @@ Options parse_args(int argc, char** argv)
       o.seconds = std::atof(argv[++i]);
     else if (a == "--iters" && i + 1 < argc)
       o.iterations = std::atoi(argv[++i]);
+    else if (a == "--slim" && i + 1 < argc)
+    {
+      o.slim = std::atof(argv[++i]);
+      o.has_slim = true;
+      if (o.slim < 0.0 || o.slim > 1.0)
+      {
+        std::cerr << "--slim value must be between 0.0 and 1.0\n";
+        std::exit(1);
+      }
+    }
     else if (a == "-h" || a == "--help")
     {
-      std::cerr << "Usage: bench_a2_fast [--buffer N] [--seconds S] [--iters I] <model.nam> ...\n";
+      std::cerr << kUsage;
       std::exit(0);
     }
     else
@@ -78,7 +97,33 @@ struct LoadedModel
   std::string path;
 };
 
-LoadedModel load_nam(const std::string& path)
+// Select a SlimmableContainer submodel for the given slim value, mirroring
+// ContainerModel::SetSlimmableSize: the first submodel whose max_value exceeds the value,
+// else the last. Returns the chosen submodel's model spec and appends a label to `path`.
+nlohmann::json select_container_submodel(const nlohmann::json& config, double slim, std::string& path)
+{
+  const auto& submodels = config["submodels"];
+  if (!submodels.is_array() || submodels.empty())
+    throw std::runtime_error(path + ": SlimmableContainer 'submodels' must be a non-empty array");
+
+  size_t idx = submodels.size() - 1;
+  for (size_t i = 0; i < submodels.size(); i++)
+  {
+    if (slim < submodels[i].at("max_value").get<double>())
+    {
+      idx = i;
+      break;
+    }
+  }
+
+  std::ostringstream label;
+  label << path << " [slim=" << slim << " -> submodel " << idx << "/" << submodels.size()
+        << ", max_value=" << submodels[idx].at("max_value").get<double>() << "]";
+  path = label.str();
+  return submodels[idx].at("model");
+}
+
+LoadedModel load_nam(const std::string& path, const Options& o)
 {
   LoadedModel m;
   m.path = path;
@@ -87,8 +132,22 @@ LoadedModel load_nam(const std::string& path)
     throw std::runtime_error("Could not open " + path);
   nlohmann::json j;
   is >> j;
-  if (j.value("architecture", std::string()) != "WaveNet")
-    throw std::runtime_error(path + ": not a WaveNet model");
+
+  // Resolve a SlimmableContainer to the submodel selected by --slim (each submodel is a
+  // full, standalone model spec). A plain WaveNet is used directly.
+  std::string arch = j.value("architecture", std::string());
+  if (arch == "SlimmableContainer")
+  {
+    j = select_container_submodel(j["config"], o.slim, m.path);
+    arch = j.value("architecture", std::string());
+  }
+  else if (o.has_slim)
+  {
+    std::cerr << "[note] " << path << ": --slim ignored (not a SlimmableContainer)\n";
+  }
+
+  if (arch != "WaveNet")
+    throw std::runtime_error(path + ": not a WaveNet model (architecture=" + arch + ")");
   m.config = j["config"];
   m.weights = j["weights"].get<std::vector<float>>();
   if (j.contains("sample_rate") && !j["sample_rate"].is_null())
@@ -244,14 +303,14 @@ int main(int argc, char** argv)
   Options o = parse_args(argc, argv);
   if (o.model_paths.empty())
   {
-    std::cerr << "Usage: bench_a2_fast [--buffer N] [--seconds S] [--iters I] <model.nam> ...\n";
+    std::cerr << kUsage;
     return 1;
   }
   for (const auto& p : o.model_paths)
   {
     try
     {
-      bench_model(load_nam(p), o);
+      bench_model(load_nam(p, o), o);
     }
     catch (const std::exception& e)
     {